Hi, I have a KX91-3 S2 mini. The drive levers don't move are locked by a bracket under the platform that toggles up and restricts movement. With both lock levers down, everything else works (swivel plus all boom /bucket/blade movements). I can operate the tracks if I disconnect the linkage from the drive levers. What controls that lock bracket at the bottom of the drive levers and what can I do to fix? Thank you very much!