The bond tech gears are grinding the filament. Then extrusion stops. But the printer keeps going because the filament sensor is still detecting filament. 

I’ve tried loosening and tightening the idler screw. But neither seems to make a difference. 

Any advice? I’m running the MMU, but it isn’t grinding. 

I have another MK3 running the same filament without problems. Perhaps there is too much friction due to the tubing on the MMU? 

I’ve tried overture, polymaker polyterra, and printer solid matte filaments.