It may be a rear spring problem... or maybe T bar adjustment. If the T bar on the same side is set a little low it can throw the back off also. After taking everything apart for a front re-build, this is possible. Suggest you re-check T bars first. The FSM process works... or trial and error. You can try cranking the T bar on the diagonal opposite front wheel up a turn or two to see if it helps without throwing the front end off.