Are all the lights, LED, Smoke and Couplers functional? Or are some out?
I don't understand your comment about goes fwd but thinks it is in reverse? Have you tested in conventional and DCS, or DCS only?
As far as stuck contacts, that is still on the table. The relay normal unpowered condition is set for FWD motion. Which is what you have.
Power up and carefully jump the FET for relay. If the relay switches, you can change the FET. If that doesn't solve it look for a burned trace and work your way back to the FET gate signal via the buffer. You can change the buffer. If not that, the processor segment is bad and the processor board needs to be replaced.
Interesting that one owner has two boards with this symptom. I don't see many failures like that. Was speed control ok on the power supplies? They normally go when the audio amp does, especially other things go wrong on the processor board. G
