We are dealing with probability here, with the interace board (the one with buttons) being the logical culprit. Unfortunately it could be the control board, or even both.
As you have probably guessed, a service tech has the boards in the truck and merely changes them out until the problem is solved, but you do not have that luxury. If you want to try to fix it you will have to try a board at a time, but I think it is likely the interface board will solve your problem. If not you will have to go to the control board.
Since both of these are pretty costly, you will need to think about whether or not try the repair. This is a pretty good dryer when it works, so I would go for it.
Good luck, let us know how it turns out.