My UpBox+ has suddenly failed. Overnight it started airprinting mid-print. This morning I retracted the filament and cut it off, and then tried to extrude again, and found that the filament wasnt being pulled in. So I stripped it down and cleaned the gears with a toothbrush (was some plastic dust, but nothing major). The problem seems to be that the gearwheel isnt spinning - it IS powered, but just kind of stutters in place. What would cause this, and is there a fix? Im in the middle of large job and really need this machine operational

Thanks for any tips,
Andy