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On linux just type "locate .def.json" Anyway you can see all of them here just as easily as ahoeben says: https://github.com/Ultimaker/Cura/tree/master/resources/definitions

Could you show a screenshot of your model in both PREVIEW and PREPARE mode please? I'm not sure what you mean by "in the middle". Do you mean that central cylindrical hole that is at the center of all the fins - do you mean that was not supposed to be empty? If so then you have an issue with your CAD model and posting the screenshots will help. Or do you mean about that tiny little hole in one of the fins? Again - it would help to see the PREVIEW screenshot.

Are the numbers sticking into the part (grooves) or sticking out (bumps)? Sticking in is usually better. If they are sticking out then the walls of the numbers are probably too thin for the nozzle - make sure the walls are double the nozzle width or larger e.g. 1mm wide. If you must go smaller make sure to check the box: "enable thin walls". And consider also lying about the nozzle size - if the nozzle is 0.4 you can set line width to 0.35 and that will work relatively well. Please show photos (screenshots).

By the way, if you are going to use blue tape, it helps a lot to clean it with isopropyl alcohol. Without doing this, the blue tape has a waxy surface (to keep the tape from sticking to itself I suspect). This comes off very easily with a single tissue half soaked with IPA.

If you saved it as a stl file then problem solved but if you saved it as a 3mf file then please upload the 3mf file here and then also if you have the energy, please report the bug in github (you have to create a github account but the rest is easy). This could be a very recent bug. This worked for me the last time I tried it (I have a version of cura a few versions ago). I could create the bug report for you but it's so much better if the devs can ask you questions on github as some of them don't come to the forums much: https://github.com/Ultimaker/Cura/issues/

Was @ahoeben correct? Did you save it as an STL by accident instead of a 3mf file?

No idea. I'd leave things as is. If I see someone contacting you as smartavionics I'll let them know.

Change "combing mode" to "not in skin". If you look at your part in PREVIEW mode and choose color scheme "line type" and check the box for "travels" (blue) you now get 2 types of blue lines - 2 colors - one color shows retraction moves and the other shows non-retraction moves. You will see that with default settings there is no retraction for the layer you show in the picture above (bottom and top layers are called "skin"). Retraction is very quiet on the S3. And fast. You have to hold the filament just below the feeder to tell if it is actually retracting or not. Or use the color trick I mentioned. What is combing? Combing saves a lot of time on a print - if for example you are doing infill you don't want it to retract hundreds of times as some stringing *inside* the part is usually fine. Unfortunately it is also enabled by default on top and bottom layers. Just change combing to "not in skin".

The next time it is doing anything strange on the bottom layer, push the bed up or down gently to learn what the issue might be.

Is this on a PC? What is the "com" port? I think there was a bug in most versions (all versions?) of cura where it only uses com ports up to around 10 or 20? You can use arduino software to load the hex file or other software - I think pronterface might be able to upload hex files onto a UM2. But easier to keep switching PCs or Macs until you find one that has the com port < 10 (e.g. COM3) Power cycle the UM2 occasionally also. Also for some people the USB on their computer just doesn't have the power that a UM2 needs so adding a USB hub could help - or again - just try a different computer.

What kind of printer do you have? I recommend only doing manual leveling. Anyway - more importantly - don't necessarily blame leveling for your head flood. Head floods are usually caused when your part is (at that moment) wider than it is tall and it comes loose from the bed. Here is more info about getting parts to "not come loose" - both *what* to do and *why*:

Some people swear by sketchup and 3d printing but they all know everything in this article. I suspect you only need to worry about the "reverse faces" discussion. Please at least skim this article quickly if you must use sketchup: https://i.materialise.com/blog/3d-printing-with-sketchup/

I recommend you avoid active leveling and just do manual leveling procedure once. Then you should "level on the fly". If it's printing with blobs and gaps like the middle of those 4 parts then it's either underextruding due to failure of some kind or you are too far from the tape. The top part has just a few traces - maybe 4 - in a diagonal line that clearly look too high from the tape. Maybe you pushed down on the bed then briefly without realizing it? If you are too close to the part it will look transparent - sort of like the right side of that top part. Although that might also be underextrusion. So my guess is all of your issues are explained by underextrusion but it will be much more obvious if you just push up and down on the bed gently whenever you see something you don't like and remember which way made each of those 4 parts better. I suspect you will find there is something wrong that is causing underextrusion. Possibly you are simply printing too fast or too cold or there is a partial clog in your core or one of a dozen other causes. If you conclude it is underextrusion after pushing up and down on the bed during the first layer then let me know here and I'll post my list of possible causes. The first thing to try is doing a few cold pulls (it's an option in the menu on the UM3).

Looking forward to seeing the video. 🙂

I don't understand - is this patina some kind of paint that changes color over more than 14 hours? I'm ignorant of painting techniques and whatever "patina" is.