I recently had a jammed Maker Select Plus. I disassembled it and cleared up the jam then noticed that it wasn’t actually pulling filament through the hot end. Upon further inspection, I found that the extruder gear was not turning with the shaft of the motor, so I tightened the set screw and fixed the issue. On the first print after that, it printed normally at first, but then the set screw issue happened again. I am not sure what to do. I have read that Monoprice started putting better extruder gears into their machines when shipping and I only just got mine at the end of November 2017. I am not sure if I am doing something wrong, or if this is a common problem. Please help!
I would attempt to tighten that set screw one more time. When you do, make sure you tighten it on the flat end of the motor. By that I mean on the stepper motor there is the part that the set screw touches. Most of them will have 1/4 of it flat and 3/4 round. If that does not work, try setting it with some lock-tight. if that still doesn’t work I would try looking for a new set screw and gear.