The other day I was replacing the upper barrel base and when I was finished I decided to go test fire it and I noticed that like every fifth or sixth bb dropped within 10 or so feet. What could be causing this to happen? Plus I can't seem to keep my left selector switch from falling off. I finally resorted to super glueing it. I'm also not entirely sure how to properly adjust the motor fine adjustment screw under the bottom side of the grip. Any suggestions?