[Styrak]

Hi there. Working on a buddy's TM MP5. It's a few years old, but still in very good shape including the internals.
The problem is, the gun isn't firing. Well it is but...

It wasn't firing so I opened it up and saw the trigger contacts were greasy and not close enough together so I washed it and bent the contacts back. Tested outside the gun and it turned the motor when I pulled the trigger.

Put it back together, put it on semi, took one shot, then nothing. Just dead. No motor noise.

Pulled it apart again, opened up the mechbox, and the motor turned when the trigger was pulled.
Put the mechbox back together, motor still turned when trigger was pulled. Put the gun back together, fired a 3 or 4 shot burst on fullauto, switched to semi, shot once and it died the same way, no noise whatsoever.

I've already looked at all the contacts and they're (obviously) making a connection, but something happens on the first shot, or first few shots.

Could something be pinching or knocked out of place or grounding/shorting out?

This is baffling me. Help?