Since only 2 of the 3 pops are locking on, it sounds to me like a problem at the pops themselves and not with the driver board, but you can do a quick test to find out.

Remove connector 2j13 ( power off ) from the driver board, then power up. If the coil still locks on, then the problem is with the switch itself and not the driver board.

I would hazard a guess that the coils will still lock on and your problem is probably the resistor and/or capacitor that is attached to each of the locked on coils. Just packing up a machine and moving it is more than enough of an excuse for these 25 year old machines to decide they are going to start acting funny.

On one of the locked coils, you can cut the resistor and capacitor at a place where you can reattach them again if they are not the problem. Clipping them removes them from the circuit so you can see whether one of these is shorting the coil. If the coil does not lock on then one or both of these is the problem. You could cut just one of these first so that you don't end up replacing both of them. Wouldn't be a bad idea to replace both of them anyway and replacing them for all 3 coils is a good idea.

Good luck.

It takes the driver board out of the equation. The pops are special solenoids and can be fired with or without the MPU. Clip the cap and or the resistor on one of the pops and I think you will find this solves your problem. If so, replace the offending cap ( 22mfd) and/or resistor.

Let us know what you find.