Print job stops extruding but the head keeps moving

Hello All, I am sorry if this is not in the right group, I am brand new to this forum. I own a 5th generation Makerbot Replicator 2x Experimental. My problem has happened many times even when under warranty. Makerbot just sent me new heads and it would work for a while then the issue returned. so now its not under warranty so im searching for help outside of Makerbot. like I said in the title my print jobs start up fine and at a random point it stops extruding but the head continues to move. I have attached some photos of the filament where the gear has worn in a half circle, have tried many brands of filament, tried adjusting temperatures, nothing on the spool is binding, I am at a loss any help would be greatly appreciated.

Attachment 10045Attachment 10046

Basically something is probably jamming the filament. This could be the temp is to low for the print speed, some restriction in the nozzle or PTFE (if using it). the first thing you could try is to slow way down on the print speed and see what happens.
From what you say on it worked for a while then started again leads me to believe it is getting a clog or something.
What temps, speeds etc. a little more info would be good.