I have had the M2 for 3 month, very happy printing different things, most of the time worked fine but some times it will just stop extruding mid way. so follow the steps to check what could be wrong:
1. Turn the filament drive fan, so you can see the teeth, try to extrude and retract, make sure that teeth still turns.
2. retract the filament, and visual exam the teeth mark, mine is not deep at all, hardly see the teeth.
3. try to turn the screw to tighten the teeth, however tighten it does not make any difference.
4. try retract and pull the filament out, extrude in multiple times, and somehow it will just start to work again.
So today I decided to solve this problem, took the filament driver out, and made a big discovery:
see the hole for the filament, which suppose to be a small hole (according to the stl file):
but it get wear out so just getting bigger and bigger:
luckily I have another spare part, so get that installed, and print another drive for backup. and until now the problem does not seem to occur at all.
so if you having similar issue, check your drive and see if the hole, I guess all drive will have the same issue over time?