If you’ve replaced all the parts you can think of, and the engine side PCB 10 pin connector is ok, top suspect would be audio portion of PS2 board. If this is beyond your scope of repairs, contact GGG ( George ) on this forum. He can fix your Dreyfus. As he has mentioned on this thread, repair board is a little difficult to fit but doable. If you’re out of options to try, I’d send the whole locomotive & tender to George for repair……the boards to fix that engine are currently available, but the supply is limited……
Pat