[version 7.0]

I recently bought a Progear version 2 gearbox for my TM M4A1. I was transfering all my internals from the stock gearbox to the Progear when I noticed something. When I was screwing down the Philips screw that holds down the cut off lever, I couldn't screw it down all the way. The same thing happened when I was screwing down my trigger assembly. I tried really hard to turn my screwdriver but the screw wouldn't go down any further. I know there is nothing wrong with the screws themselves because they worked when I tried them on my stock gearbox again. I think it's the fault of the Progear. Any help would be appreciated. Thanks!