Run into this a lot with saturated (moisture) filament that hasn't been properly stored. Which for me is a lot of my rolls of filament.  The steam creates back pressure and acts just like a clog.  Try the old oven trick.

Thanks. It is definitely worth a try. It's in the oven now, I'll see if it works better after baking a few hours.

It will print perfectly OK for a while, and then at some apparently random time, the filament will stop feeding through the extruder. I don't hear clicking like it is trying and failing to push the filament through, it just stops coming out.

I thought it might be a clog, but when I switched back to the natural filament I had been using, it feeds perfectly well, and was able to print the entire object (which I'll now need to figure out how to paint :-). There was no dust in the gear that needed to be cleaned out either.

The only thing I can figure is that the filament has occasional thin spots every few feet and sometimes it just can't be grabbed enough to feed through. Does that sound like a reasonable theory? Anyone else ever seen this symptom?