@Kjetil: It may seem paradoxal, but these symptoms have a high chance to be resolved by tightening the extruder arm. In my case it was not different: the extruder was filing down the filament with nothing coming out from the other end. In case the hotend gets clogged, the filament shouldnt get filed down but rather the extruder stepper should start skipping steps, otherwise you have too little tension per se.Kjetilei wrote: The extruder arm is tightened so much that I have to force the filament in and it's not slipping as such but the stepper tries to turn the axle but fails. With the filament stuck and the stepper's constant "micro movements" the filament is eventually "filed" down.
There is a good way to adjust this after you clean the nozzle: gradually increase the tension in the extruder arm until the stepper starts skipping steps when you extrude. Reduce the tension slightly and this should be good