On and off I've used Tinker FW in my UM2+ for about a year.
On and off I've had a strange behavior as my printer sometimes pauses while printing and starts to retract filament with different speeds from time to time.
Sometimes it doesn't retract the filament all the way out and then loads filament back in and continues to print.
Sometimes it retracts the filament all the way out and thus can't load it back in and then starts to print without filament.
Every time this has happened it continues to print, of course sometimes without having any filament.
This has happened maybe 10-15 times over a one year period.
Yesterday it happened again, with "full" speed it retracted the filament all the way out but I heard it so I was quickly there and put the filament back in and saw to it that it got loaded back.
Then I noticed something else, it skipped a layer or two, see picture. This has puzzled me in the past. A few times I've had prints like this, unknowing of the reason. I have blamed the filament or the nozzle thinking it had clogged and loosened upp again after a while, but quite possibly it is this phenomena that is the culprit.
I wish I could remember if the bed lowered a bit and if the head moved to a specific position, but i think it just stops where it is at and does its thing.
I am currently on Tinker 19.03.1 but have had the same issues with 18.11.1 and 17.10.1 as well. And to be totally honest I cant to 100% rule out that it hasn't happened with original FW too. I really should have paid more attention to this but in the heat of the moment I get really upset thinking all kinds of nasty things. Then the next day it's business as usual and (almost) all is forgotten.
I have only read about one other person having had this problem, are we really the only ones? Cus then it sounds more like a hardware error to me.
Previously I have wondered if I'm causing this when I shift between using S3D, Cura, USB and SD, but since the last time I installed Tinker FW I have ONLY used Cura and have been printing exclusively from SD cards, I have not had my USB cable inserted into the printer since.
After I installed Tinker I made a factory reset on the printer, as I always have.
On a few occasions I have started the same print (gcode) again and it has printed correctly.
Approximately 20 seconds after this particular print started again it was at a height of 52.20mm (according to info in display).
I'm not very keen on trying this print again because I made some error with the model (so I wont be able to use it anyway) and my experience is that it will work when trying a second time. Plus its a 10hr print.