I have a Clark C25C, when truck is in drive or neutral and stopped with inching pedal engaged, it will creep backwards when you start to release the inching pedal. It will do the same with the brake pedal. If I unpin the inching pedal from the transmission, it will actually creep forward when in drive, but the brake pedal will still creates the reverse creeping scenario. I have swapped all the relays, and the situation does not change. Any ideas where to look instead of a Transmission rebuild?

Thank you kindly for your help!

Joe