Check everything in the first post. That covers 99% of the issues.

Rebuild your pre-assembled shocks and diffs....they are never 100% properly assembled. they are usually low on fluid and in many cases, the shock bladders are not properly installed, and the piston retention screws are not threadlocked.

Buy rcshox's garodiscs instead of using the stock slipper pads. If you feel the need for even MORE grab than those offer, invest in Mac the Knife's clutch basket.

Don't bother mounting the stock tires to the rims unless you're using them on asphault.