So I had a clog in the extruder gear, so I disassembled the hot end and extruder and I got the filament out and went to reassemble the gears feeder and hot end and I have an extra screw. It’s shorter than the screws that holds the gear assembly, but the same size Allen key to remove it. I am kind of baffled to where it goes.
All four screws are used to resecure that part, though I’m not sure which of the four gets the short one! I’d just run a long screw into each hole until I find the one where it won’t thread in all the way. That’s the short screw hole 
See also this wiki page: P1S Abrasive Filament Extruder Upgrade Guide | Bambu Lab Wiki
From the videos I watched to secure the hour end and gear box back there is only 3 screws. Idk