Here’s an interesting one…
The big gear on my E2/T1 stripped at the hobbed shaft. The stepper still spins the big gear, but the hobbed shaft does not advance filament. Since the delrin gear is press fit onto the hobbed shaft, the metal splines defeated the plastic.
Here’s a clip demonstrating the issue:
The issue looks like heat creep, clogged nozzle or starved extrusions.
Suspected root cause: Front plate of dual extruder screwed on too tight and bound hobbed shaft.
I probably re-installed the front plate too tight after disassembling to remove filament from the extruder. Once the end of the filament passes the hobbed shaft, the only options are to grip and remove with pliers/forceps or push the filament further into the extruder to make room for a new filament. Anyway, I probably screwed the long screw too far into the nylock and bound the hobbed shaft.
If you’ve removed the front plate of the Dual V3 to clear filament, check that the two screws aren’t on too tight.
I hope this saves someone time… it was a frustrating two weeks and half a spool of troubleshooting.