Boxes tend to move lower than desired when tightening the screws. Even if you use a c-clip to hold them in place. Phillips screw heads tend to come off because it's difficult to maintain a precise angle when tightening. Screws tend to change angle to follow the texture of the wood in the studs. I swapped the screws for torx screws to solve the wire stripping problem. It is better to replace crates than to build new ones. Once the box is screwed down, it is difficult to put it back in its original position. If it goes in too deep or not deep enough, you will need to drill new screw holes with metal washers. Otherwise, the screws will simply "find" the original holes, and the box will return to its original position.