bizarre problem w/Creator. Suddenly won't print to certain area of the bed.

[roykirk]

One of my Creators (my oldest one) has developed a sudden and perplexing problem. When it gets anywhere near the left third of the print bed, the extruder starts "chattering" and it stops extruding filament. Once it moves back towards the right side of the bed, the chattering goes away and the filament starts extruding again. I did a test where I put it in "load filament" mode so I could move the extruder around freely while filament was spooling on the print bed (with the print bed fully retracted to make sure I didn't have a leveling problem). Sure enough, when I would slide the assembly over to the left side, extruder starts doing the same thing and the filament stops. I've never seen anything like this, and it's especially bizarre considering that it started suddenly. I've checked to make sure the filament isn't binding on the spool for some reason when it gets over to the left side. No problem there as it is coming off the spool easily. Anything else I can try as I continue to troubleshoot this?