I'm using a makerbot replicator 2 with PLA, currently trying to finish printing a VR headset (roughly 8 hour print). I'm using a .17mm thickness, 90mm/s speed, 10% infill, at 220C. This problem has occurred on previous builds, but we always managed to 'fix' the issue, which was typically that the stock filament holder is crap and lets the filament get bound.

I originally thought this problem was due to a clogged extruder head or my filament getting in a bind; however, I've thoroughly cleaned the head, balanced my build plate, and I've watched my rig print through surprisingly difficult tangles on my filament spool. I really can't come up with what I think is happening to cause this problem, but sometimes I get a really poorly printed layer or two in my builds, often forcing me to scrap the entire thing and restart. If I catch it in the process, the most recently printed layer looks like a torn up spiderweb of just really thin strands filament everywhere.

I can't fully rule out a clog/bind/out-of-balance plate, but I can say that I've done everything I can think of (within reason; I can't really unwind enough filament for the job and stand there and hold it the entire time) to rule them out including multiple relevels, stripping down a stranded copper wire so I can force it through to clean the extruder nozzle, and loosening the filament on the spool every fifteen minutes or so. If you're convinced that it's still one of these issues, please provide a way to solve, as none of the standard methods seem to work.

Images include view of a top layer during failure as well as a side view of a bad layer sandwiched in between viable layers. All advice is appreciated.side view.jpgtop view.jpg