makes some horrible noises and that big lump at the end of the filament isn't good either. could easily get stuck in the hotend.

The extruder is jamming.
Looks like the feed path has issues, the mumu clearly thinks it's working.
I'd strip the extruder down and check all my bits of ptfe were in the right place.

Either that or the filament is being held by the mumu and not allowing the extruder to actually feed it into the hotend.

The complicated bit is working :-)