M4 selector switch jumps out of semi auto

[Opossum]

So I'm rebuilding my M4 and I hate gearboxes...

The gearbox is from a fully functioning G3, so I changed the trigger, selector plate, safety switch etc. The M4 body is King Arms.

When I switch the gun to semi auto it'll fire but the switch will jump around clockwise towards auto and the trigger will lock. It works fine in safe and auto. The only thing I've noticed is the selector switch hole in the KA body is 0.5mm or so further rearward than one on a cheapsoft M4 I borrowed as a comparison.

There's nothing jamming between the body and gearbox and the selector switch isn't exactly loose.

Any ideas? When switching from safe to semi the trigger feels a little solid before it pulls, as if it's catching on whatever makes it "safe" before it moves, but moving from auto it fires fine but kicks the switch clockwise. I'm guessing it's something to do with the selector plate/selector switch interaction but there must be a bit of force involved for it to kick the selector switch around. It moves about 25 degrees clockwise.

Cheers!

[Edit:] I'm not sure what brand gearbox it is. It's just a generic V2.

[Opossum]

Re: M4 selector switch jumps out of semi auto

Fixed it. I was using the wrong safety lever inside the gearbox. I was using one with a longer "prong" that pushed the selector plate too far rearwards.