I'm telling ya IT'S THESHOCKS!!!!!!!! 
(they first came out with those krappy shocks as an upgrade part offered on the Mini-Baja (second generation mini-t), and have included them on everything they've released since (Mini-Slider, Mini-Late Model, Mini-Desert Trucketc. - and they've been problematic from day one, as they don't seal very well and lose oil and the shock shafts are spindly and very knotch-ey feeling)
Get the allow shock kit and your problems
will be resolved, I promise.
storing it "off the wheels" not only keeps pressure off the shocks/suspension, but also keeps the tires from flat spotting