I would get out a micrometer and check that the filament is uniform in thickness. I have two more than half full rolls I set aside. They would work perfect and then all of a sudden this exact thing would happen. It was too hard to push through the extruder and the hobbled bolt would chew enough material off that there was no way the filament could continue.

Over sized filament can do this very easily. A .1mm difference in size is probably enough to make this happen, but that amount will vary from machine to machine.