All I can assume is that the print head collided with the print surface and damaged the side of the nozzle.Had a problem this morning - the print wouldn't stick to the build plate on my big Anet printer - I thought it was a levelling problem, but no, whatever I did the filament wouldn't stick & created plastic brillo pads! Thought it may be the filament, so I opened a new shrink wrapped spool of PLA. Whilst I was loading this & purging the old filament, I noticed that when the filament came out of the nozzle, instead of dropping as a thin thread, it came out & curled round the side of the nozzle. I tried cleaning it, but eventually had to change the nozzle - a tricky procedure, as it has to be done with it hot - about 230C - bad enough getting the old one out, but putting in a new one! Despite being careful I still managed to get a few burnt fingers. I obviously damaged the original nozzle somehow, and it wasn't pushing filament out correctly. I'm mystified, as it was printing OK yesterday, and the only thing I'd done to the printer, other than turn it on was change the micro-sd card!
Dave
Print nozzles do also just fail, sometimes spectacularly, and the filament that was still in it hid the damage until it heated back up again.












