I'm assuming the problem is there's a hole in the cover there that doesn't completely clear the switch built into the interior of the case so when you tighten it it's pressing down on the switch? If I'm understanding correctly (your pic isn't really helping

), a couple of options come to mind. If you have one, dremel the hole to be a bit bigger and clear the switch, or like you said, simply don't tighten down that screw since I'm sure there's more than enough available to secure the cover.
I would probably call the case maker and possibly getting a replacement top (doubt it's worth RMAing the whole case over), since if the switch is actually built into the back, then it seems like a manufacturing defect for the cover not to clear the switch properly.