sounds like something on the servo saver is not set right. Ive had the 3.5, and the 8e and the only issue I had was the 8e arrived with the servo saver set way to loose.
can you post a pic?
Washers sound like a good idea on the diff screws. Either that, or find screws of the same length/thread but with a larger head. Many hardware stores have a isle that is just boxes of screws and hardware. And there is often a gauge that you can put your bolt or screw into so you can find the diameter of it.