I've had my UM2 for about a week now and printed a lot of smaller objects (up to 4 hours print time) without (much) issues. However I'm trying to print a bigger object (24 hours) and it's happened twice already that when I get up, the printer head is just waving around in mid air because the filament broke.
The coil is not stuck as far as I can see, if I pull on the wire it doesn't seem to require more force than before.
It also doesn't seem to be a "grind" as the break was clean (the first time, I haven't had time to check this morning). But it did break exactly on the feeder sprocket twice. I am using the transparant PLA from Ultimaker for this print.
Any ideas/pointers? Also, how can I get the filament out from the bower tube, last time I've just pushed other filament behind until the broken piece was gone but it took half an hour or so.