If I understand the problem correctly, when that happens to me it is usually because there is a bit of filament debris caught between the gear and the hotend or the roller. That can be fixed by disconnecting the feed stepper and cleaning the gear and the inlet to the hot end. In really bad cases I've had to remove the nozzle and stepper, heat up the hot end and push the filament slug up from the bottom of the hot end toward the gear.