gr5

Oh an easy question!  Yay!
 
So this is from memory but I think it's under "maintenance" somewhere and then "calibrate lift switch" (the switch that lifts the right side print core).
 
The procedure is extremely simple and quick.  At some point you just push the print head around until the lift switch is in that slot and click a button.  That's it.  Do it a few times and test as it's trickier than you think but it's pretty darn simple.
 
There is also something called "reset to factory defaults".  Something like that.  That resets *all* of these positions.  I don't know how this could have been messed up other than a bit got flipped somewhere so I'm wondering how many other things are messed up on the "hard drive" (it's a solid state drive).  I wouldn't do "reset to factory defaults" unless there are other issues because then you lose all kinds of useful information and have to calibrate lots of other things.
 
Occasionally, on these printers with SSD, you have to reinstall the firmware.  Yes the SSD remaps all bad blocks but it doesn't know what the old values were before they got corrupted so you have to reinstall the firmware occasionally.  Everytime you update the firmware it also reinstalls all the firmware and will do so into the remapped "good" blocks on the SSD.

Just heat the nozzle to about 120C in the menu on the printer.  Open the door and clean with a tissue or paper towel.
 
More importantly - this is called a "head flood" and you got the most mild version ever but it can be a disaster.  It's never happened to me but it happens a lot - especially to people who have printed fewer than 100 prints.
 
The fix is to get your parts to stick better to the bed.  Ultimaker has much advice on this.  I have a whole video on this on youtube.  The main tricks:  squish, temperature, brim, rounded corners, glue.  I talk about each of these for many minutes as they are complicated and it's good to understand.
 
squish, temp, brim are set by the ABS profile by default.  Don't skip brim if your parts aren't sticking (I don't use brim except very rarely for the most difficult of prints).  So if you haven't messed with profiles you probably just need to worry about the last issue, glue.  I recommend Magigoo.  They have a product specifically for ABS.  Get that.  It will save you major headache (no head flood).
 
If you have 20 minutes, this video will teach you a lot:
 

Do you have the latest firmware on your S3?  I believe some network improvements were included a year or two ago in the S3 firmware.
 
I believe, in the menu somewhere on the S3, there is an option for something like "digital factory reset" or "network reset".  Something like that (and they changed the name of the option a few years ago I think).  That resets a lot of things - not just the network connections.  This can often fix issues like this.
 
Also in cura you can manually tell Cura to search for and reconnect to your machine.
 
If you are using digital factory I don't think it does a local LAN connection but connects out on a server on the internet somewhere.

It's called a prime tower.  I recommend you don't disable it.  Everytime the printer switches to the other printcore, on the way back to printing, it stops at the prime tower and extrudes a bit to "prime the pump" as they say.
 
You can print without the tower but quality will go down a bit.  There will be a little stringy sausage bit attached to one of those 3 parts - one sausage on each layer where it changed printcores.
 
The tower stops when the support material stops.
 
Or you could use the primary printcore to make the support and then the prime tower will not be printed at all.
 

It's definitely not just you.  My friend got the same message today.  Someone said that after a few hundred people download the new cura, microsoft will decide to stop doing this message.  Just "run anyway".  I suspect it's more than a few hundred.  But within a few days I think it won't do this anymore.

Are you talking about the staircase steps nature of your curved top surface?
 
If so then you need to decrease your layer height.  I can't quite read your layer height but I think it says 0.4mm?  You can reduce that to 0.1 and still get good quality.  The limit (before you get diminishing returns) is around .06 or .08mm (less than 0.1mm - I clarify as people often accidentally add or remove a zero, including me).
 
But 0.1mm layer height will print 4X slower than .4mm layer height.  So there is another option - you can do thicker layers up until your first "top" layer at the bottom of that curve by using adaptive layers.  Check that box.  If you want layer heights to be .4mm in the bottom portion (to save hours of time) and the thinnest layers to be .1mm then you need to find the average and difference of those two values.  The difference is .3mm and the average is .25mm.  So in this example (.1 to .4) set the layer height to 0.25 and set the adaptive layers maximum variation to .15mm.
 
ironing will only smooth each of those flat "steps" in your image above.  And it will waste lots of time.  You have so many steps that I think ironing is probably not worth the extra print time.  You can experiment and decide.  Ironing is tricky and you may have to play with the parameters a lot to get best results so if you play with ironing you should do it on a small part first (say 2cm by 2cm by 5mm tall).
 
By the way, all the yellow shown in your picture are thought as "top skin" or "top layers" by cura.  Each and are thought of as separate surfaces - separate layers.  Cura tends to mostly think of one slice at a time.  So when it is doing that middle yellow strip that portion is a "top" (aka skin) layer and then there are other portions of that layer that are not skin which will be other colors (but hidden from this view by layers above).
 
 
 

https://support.makerbot.com/s/article/1667337917781

The secret word is "combing".
 
You want to disable combing.  And you want to make sure it's really really off so there are probably 2 or 3 other combing settings.  Combing is the word that describes movements within the walls - movements in areas where you normally have infill or shells.  Note that even when you disable combing I think it still combs if the distance is below a certain distance?  Or maybe not.  So here's how you test it before you print:
 
Go into PREVIEW mode after you slice and scroll throught the layers.  Make sure you are looking at it with color scheme set to "line type" and make sure the travel moves (blue) are enabled so you can see them.
 
Now light blue travel moves are retraction moves (this is what you want).  Dark/saturated blue travel moves are non retraction moves (bad - creates internal stringing).
 
Make sure you tweak the settings until all (or 99%) of the dark blue lines are gone.

It's hard to see what's going on so it might be best if you post the project file.  In cura do "file" "save project..." and post that file.
 
So you may have errors in your model - particularly tiny holes or "inverted normals".  Which is particularly common in models created with blender or sketchup.
 
But I'm going to guess you are having problems with thin walls.  Make sure "print thin walls" is checked.  And look at some of the options in the "walls" section.  Particularly:
minimum wall line width  (walls must be double this I assume) - not that there are 3 features with this or similar name so check all 3
minimum feature size
 
If what I told you doesn't help then post the project file.
 

Oh!  It's very likely arcwelder.  I don't know that the UM3 (nor the S3 - don't get them confused) supports arcs.
 
Yeah - I see lots of G2 and G3 commands in your gcode.  I doubt I had those in mine.

If you look in PREVIEW mode at your sliced model in cura, set the view mode to "line type" and make sure the "travels" are checked (blue).  The travel moves come in two colors - light blue and strong/saturated blue.  Light blue is a retraction move.  darker blue (as shown in MariMakes photo)  is non retracting.  There are quite a few settings that can control which type is chosen so if you have this problem again, check the blue colors and then look at all the retraction settings.

https://ultimakernasupport.zendesk.com/hc/en-us/articles/115004226246-Printhead

Marlin is expecting a very simple circuit where there is a 4.7k or 47k (depending on which sensor table you use) resistor in series with the temperature probe.  But the Ultimainboard V2.1.4 which goes on the UM2 printer has an op-amp circuit that is much more complicated and designed specifically for PT100 resistors.  I recommend PT100 resistors as they are great.  They are cheap, can be tiny, and come in all kinds of sizes.  And every PT100 resistor table is identical to every other no matter the manufacturer.  Unlike normal thermistors.
 
However it might be possible to create your own resistor table.  Maybe.  I'd look at the circuitry first and figure out what resistance results in what voltage at the "arduino" first and then from there you could use that info plus the thermistor table you have.  You might find that when the temp gets above or below a certain temperature you are at the full scale reading of the ADC so it might not be possible.

I just jumped into this thread for the first time and didn't read much of the posts (sorry) but I have 2 important points:
 
If the border is perfect and the interior not great then it's probably not a leveling issue.  Also this printer has active leveling which, if it doesn't fail with an error message, usually works perfectly every time.  Again - if border is good - leveling should be good.
 
Failures a few minutes into the print are usually caused by the front fan failing or an issue with the teflon in the core either not long enough, or interior diameter too large either of which can cause the filament to get stuck in the teflon section (inside where the cooling fins are on the print core).
 
Don't get the front fan confused with the 2 side fans.  The front fan cools the print cores.  The side fans cool the plastic part you are creating.
 

Please post a picture.  90% of issues with PVA is due to insufficient drying.  Despite using lots of desiccant I have to dry my PVA before every print.  I set the heated bed to 60C. 
 
I look in cura to see how many meters are needed (in bottom right corner hover over on the "i" in the circle).
 
Then I unspool that much and put it on the hot glass with the spool on top of that.  Let it dry for 4-8 hours before printing.  You should see different results.
 
Please post a picture.
 
Wet PVA prints snowier.  Whiter.  Dry PVA is clearer.  Very wet PVA sputters and crackles and you can see the steam.
 

So there are a few possible causes on a UM2 but 90% of the time the set screw on one of the pulleys comes loose and usually the stepper motor pulley.  So determine which axis it is and then push the head around and see which pulleys move when you slide that axis.  I assume the Y axis as I assume it was positioned as shown in the photo.  Anyway start with the stepper on that axis and tighten the hell out of the set screw.  Hopefully you got one of the UM2 printers that came with the green and black hex driver and you can use that because it will reach behind the covers down to the stepper.  Just push the head around until the screw is accessible.
 
If you only have one of those little L shaped allen wrenches make damn sure it's the right size (2mm hex) because you will strip the head if you don't have the right size because you will be tightening HARD.  So you want to twist so damn hard that the steel shaft of the tool twists a little.  Scary tight.
 
Get the other pulleys as well but the stepper one is usually the most important.  One axis has 5 and the other axis has 6 pulleys.  The one with 5 has kind of two pulleys bonded together.
 
If you only have an L shaped wrench you can remove the cover with only one or two screws (depending how old the printer is).  Don't remove the panels!  Just the corner cover.  But you won't have to bother if you have the hex driver.
 
If you don't believe me (many don't - not sure why) then use a sharpie to mark the shaft and the pulley and the next time it skips a layer, check the markings and you should see that the pulleys (all 6 of them) moved a little versus the shaft.

This is underextrusion.  It has many many possible causes.  The most common is printing too cold and/or too fast. 
 
1) Are you using default profile settings?  Have you changed any of the temperatures or speeds?
 
2) If not I'd do a cold pull of the nozzle of core 2.  Especially if this is a BB core.  For a BB core do some hot and cold pulls as described in the maintenance menu.  It will help you with the procedure.  The purpose for all of this is that plastic can caramelize in the thinnest part of the nozzle (the last few mm above the tip) and make the diameter of say a 0.4mm nozzle become a 0.3mm nozzle which increases friction and causes underextrusion.
 
2b) Another thing to try is to put a different core in slot 2.  Your printer should have come with two AA 0.4 and one BB 0.4 cores.  It's okay to use BB 0.4 cores with PLA.  Just slice for AA 0.4 and when you go to print it will complain that you have a different core and hit "ignore".
 
3) Feeder.  I'd test the feeder.  Pull the filament out of the print core so you can see it in the bowden.  Then go to "move material" (it's in the menus on the printer front - look around - maybe it's called "move" but make sure for second core).  No need to wait for it to heat up.  Turn the dial and the feeder moves the filament.  Now while doing that, fight the material below the feeder: pull down hard with one hand while spinning the knob to move the material with the other.  You shouldn't be able to stop the pull.  Unless you are very strong.  Typically the feeder pulls with about 7kg or 15 pounds force.  Anything over 9 pounds pulling force I consider "working fine".  If you have lead weights you could old around 10 pound weight (or 7 or 8 pounds) and sort of grip the weight against the filament and then try not to add any more force up or down.
 
Many issues are on the feeder end.  Many issues are on the hot end.  It's good to at least winnow the possibilities.

Cura said that?  Well I see two possibilities:
1) That particular filament has large particles that will clog a 0.4 nozzle so it is just not allowed.
2) Possibly there are no profiles for that filament and the CC 0.4 so you could just choose a generic PETG profile or you could choose a CC 0.6 profile but change line width (all of them - there are like 6 of them) to 0.4mm.
 
So I looked on their website and I so no mention of minimum nozzle size.  I'd email them.  And if they say 0.4 should be fine then just use the CC 0.6 profile and change line width.
 
These profiles are typically very simple - just use another one and change line width.
 
 Or you can even slice for "generic PETG".

You want to repeat a layer or two so it prints the exact same thing 2 or 3 things without the Z moving?  
 
Oh wait!
 
You want it to print exactly normal except the Z axis doesn't move for 2 layers.  Well that's pretty easy to just do it by hand in the gcode.  Search the gcode file for the letter Z.  Once you get past the first few there is only one Z in the file per layer and it's the height.  Just take a look.
 
Unless you have zhop enabled.  If you do then that's unfortunate as there could be tens of thousands of Z's in there.
 
But most of the time there is only one per layer so if you have 50 layers you only have to edit at most 50 numbers/heights.
 
Take a look at the gcode!  It's not that complicated.

Let's talk about #2.  This is a critical issue and the most important one and the easiest to fix.
 
There are many ways to prepare the glass.  Since you mentioned the glue stick let's use that.  spread it around sparingly in the area where the print and the tower will be.  Then take a napkin or tissue, wet it, and spread around the glue.  This will also remove 90% of the glue which is great.  You want a very thin layer.  Thicker layers of glue don't hold the part as well as thinner layers.  If there is no glue at all then it won't stick so well either (and the glass would need to be cleaned after every 10 or so prints to keep dust and oils off).  I usually only clean the glass about once per year as I have many thin layers of glue.
 
Oh - and while doing this set the bed temp to 60C because you now probably need to wait for the wet glue to dry.  At 60C it takes maybe 2 minutes.  If you start at 20C then by the time the bed reaches 60C it may be dry.
 
Leave the bed temp setting alone.  I believe 60C for PLA is perfect.
 
1) This is normal.  This is basically the purpose of the prime tower.
4) This is normal.  PVA burns (caramelizes) very easily.  Caramelized PVA is the leading cause of BB core clogs and results in the need for many hot and cold pulls on the BB core if it gets clogged or has a partial clog causing underextrusion (not a problem for you I think.  Yet.).
 
5) You should be using engineering mode if you care that much about part size.  And I also recommend 0.1mm layer height (not 0.06 which can cause quality to be worse - sometimes).  In the profiles there are some that are "engineering mode".  These give you MUCH better dimensional accuracy but also lower quality visually (more ringing noise around letters and corners).
 
3) "top" surface?  Do you mean outer surface?  maybe take a picture and circle what you mean?

If it were me I would do #3 to prove that it is the power brick.  These things do indeed go.  And when you are convinced this is the problem then get a new one.  There are two types:
GST220A24-R7B
GS220A24-R7B
 
The GST one is almost certainly what you have and puts out a little less current so I prefer the GS one.  But the GST has some improved safety features.  But again - puts out a little less power.  Even though they are both rated for the exact same power, the GST turns itself off when you surpass a threshold and this threshold is lower for the GST.
 
More info about how to setup the power budget in the tinker firmware:
 
 To me the power budget feature is very simple but it seems to confuse people.  The power budget feature does not know how much power each element uses so you just tell it.  Tell it how many watts everything is and what the budget is and it will make sure heaters are turned off or turned down a bit when they would exceed the budget.  The bed gets lowest priority.
 
In this version of Marlin is a power budget system.  Set the bed to 150W (that's what it's supposed to be I think) and set the nozzle to 25W (if you have 3rd party nozzle such as 3dsolex then set this to what is truth - what nozzle actually is).
 
Then if you set the budget to 175W (150+25) the power budget won't do anything and the printer will work normal.  If you lower the budget to 150W then the power budget will lower the power to the bed when the nozzle is on.  This changes many times per second (adjustments of power to nozzle).  All the remaining power goes to the bed if the bed wants it.
 
So for example if you use 150/25/150 as I mention above and the nozzle is on at 50% (12.5 watts) then the bed will only be allowed 12.5 watts below budget (150-12.5 is 137.5 watts) and so the bed will never exceed 92% power at that time.  This changes 20 times per second (nozzle asking for more then less power, bed occasionally restricted a little bit).