I would say its not an easy answer as shown.
1. Remove front shocks and cycle suspension. If its not smooth like butter sliding across a hot pan you have an issue. If it is then its the shocks.
2. If its not smooth keep un bolting items till you find out what is causing the binding.
A couple of us have found that rpm arms need to be trimmed front to back. The part of the arm that slides around the diff cases in which the suspension pin holds the arm to the diff. This part can cause binding.
A lot of rc's that spend more time broke then running. LoL