agm M4 gearbox lock up

[bunjieben]

Anybody got any ideas why my bros AGM m4 keeps locking up??? It seems to lock up either half way through the piston travel backwards or it'll compress the spring fully but just not release.

We've tried re-shimming it, replacing the spring with a down graded one, new gears, new anti reverse latch, 3 different motors, 6 yes 6 different batteries, new bearings, a complete re-lube and even a different casing!!!

Its been in pieces so many times its driving me insane.

Any advice will be greatly appreached