Filament binding up

The filament, nGen in particular, has bound up twice on the reel, and stopped feeding through to the head. The head continues printing, but it can’t pull the filament, so of course it doesn’t print anything and the job is ruined.

Since the first time this happened, I have tried really hard to prevent it, but it has now happened again. I tape off the reels when I change them so they don’t unwind. I inspect them before each print to make sure there aren’t any obvious overlaps. But its like a loop flips goes over another one sometimes and then gets pulled tight in such a way that the filament is caught under it.

Does anyone have any tips on how to prevent this from happening?