Sounds like some kind of alignment issue. I assume none of them are missing any parts, so I'd have to troubleshoot them myself to really give you a conclusive answer.
One thing that really popped into my head though was a M4 I was working on a while back that had a very similar problem. The gearbox seemed to be sitting to the left in the lower, so what I ended up doing was taking two lengths of zip ties, cutting the heads off, and gluing them together. I then slide them in between the gearbox shell and lower receiver. Fixed my problem perfectly. Might help, might not, but it's worth a shot... Just something to push the gearbox to the opposite side.
Just kinda spit-balling ideas here, as I've never heard of that problem in a G36 before.