Did you check that right front shock off the car? Even if they are adjustable, if there is a bad seal they will do this.
Other than that, Tell us about your suspension. Stock, Ladder, 4link? Are spring/shocks set narrow in the rear? What kind of lateral link do you have, and how high or low is it? Anti roll bar? Pre loaded weight on cross corner springs? Spring rates?
With out knowing much about the car, my list of maybes would be bad shock, preloaded right rear and left front spring, no anti roll bar front or rear, too low a instant roll center in the rear for the center of gravity.