Mecanum Alignment Problems

[Team3324]

So we have made an awesome chassis this year with in frame gearbox's. We took 4 hex Nano-toughboxs from Andymark and disassembled them so that they could be put back together inside our 1.5 x 3 inch aluminum tubing (see picture). The Gearboxes work great, but that's beside the point, not all of our mecanum wheels aren't applying pressure to the floor equally. Furthermore the internal gearbox design doesn't allow for adjustments with moving the shaft up and down to level the robot. In the picture its the front right and back left that aren't touching as much as the other two (although they are touching). This makes us not move much on that parrallel but move fine on other vectors. Anyone have any suggestions how to level the robot? we are at a complete loss.

-Members of Team 3324