So I recent dropped new upgraded gear boxes into my AK's, and have encountered a problem, with both. The selector switch will switch to full auto just fine, and when I pull the trigger, it shoots on full auto. But once I release the trigger, and give it another squeeze, it only shoots semi(without me moving the selector switch). And when I switch it to semi, it works how it should.

Any ideas on why my full auto keeps changing to semi on me? Did I just f something up with the selector switch?