As per attached pic. The filament has caused a channel in the feeder arm to be ground out. This stops the filament feeding properly and means it grinds.   We have over 20 UM3's in our lab and it has just about happened to all of them now. We have swapped the arms on feeder 1 and 2 but are now looking at having the replace the arms.   Does anyone know if you can just purchase the arm pieces? We only seem to be about to find the whole feeding mechanism and it's expensive to rep