Every filament feeder keeps skipping
Originally, the printer couldn't print because of a jammed PTFE tube. Once I cleared it and tried to print something, it worked fine.
As a test, I decided to switch filaments from 2 to 3 (through Tune>Change Filament, all filaments are PLA). Ejecting the filament worked fine and the filament even loaded successfully to the nozzle, but the moment it tried to purge the previous filament, it made horrible grinding noises of the filament slipping out of the tooth gears. It never printed again since.
It happened on both sides too and no amount of pressure readjustment (through the spring mounted screws, helped. It only made the steppers more prone to skipping themselves). It seems as though the feeding of the filament is out of sync between the MMU and the extruder steppers cuz the filament seems to be pulled from the MMU, but looking through the little window, it seems as though it's also getting pulled from the extruder. I cleaned the toothed wheels to not much success.
It seems like a synchronization issue, although I have no clue on how to go about this. If I bypass the MMU and feed filament straight into the hotend, it grips the filament and extrudes just fine.
RE: Every filament feeder keeps skipping
Check the filament sensor of the extruder. If the extruder does not register the filament correctly and consistently during loading and unloading the MMU does not know when to pull respectivly not to pull the filament and works agianst the extruder. As long as you did not change the lenght of the PTFE beween MMU and extruder that seems to be the most likely cause.
See: https://help.prusa3d.com/article/ir-filament-sensor-calibration-mmu2s_2245
If at first you don't succeed, skydiving is not for you.
Find out why this is pinned in the general section!