Our team has been having some problems with one of our drill motor gearboxes. The problem was that one of the clutches was slipping quite easily even though it was set to the highest setting. 
We disassembled the clutch mechanism to discover some missing parts. Luckily we had these parts on hand from spare FIRST gearboxes. 
It occurred to me that this may not be an isolated incident. I just want to be sure no other teams are having this same problem. We discovered our problem when one of our gearboxes exhibited a clicking noise while under modest loads.
Upon disassembly we found the steel plate that resides between the clutch balls and the clutch spring was missing along with the plastic part that holds the index spring in place. When we got this gearbox we also notices that one of the two screws that holds the whole clutch together was missing.