extruder motor randomly stops responding, resumes after adjusting filament
I have a 14 month old MK2S, and in the last few weeks have started to have problems with the extruder motor randomly stopping altogether. This is leading to some prints where extrusion stops for a layer or two and then resumes, and many where, after 1 minute to 5 hours, extrusion stops for the rest of the print.
This seems different from nearly every similar extruder issue I've read about online:
The nozzle is not plugged, and the motor isn't grinding the filament, or rocking back and forth.
The motor seems to be getting a signal, as I can hear a soft electric hum when an extrusion command is given, but the motor does not move at all. If the motor is turned by pushing or pulling filament through, it will usually begin responding like normal.
I have tried tightening and loosening the filament idler screws, but this doesn't seem to affect it.
I am unsure whether this is indicative of a driver failure on the mainboard (from pulling out filament manually too harshly?), something with the wiring (though the fact that it resumes with filament motion, not adjusting the wires, makes me doubtful), or the extruder motor itself (though they are said to be hard to break).
Does anyone have suggestions for how to fix or atleast diagnose this issue?