sorry mine has a crook mpu .. i can only help with things i can check with it powered off
No worries.
I swapped the solenoid driver board over with the one out of my Flash Gordon. Didn't make any difference but at least that's one more thing of the list of potential causes.
I did a solenoid test with your mpu and driver board connected together on the test bench, plus i triggered each switch individually as well and made sure only one switch was showing up on the display at a time. I do this before sending any board out, even if a set of boards comes in for a solenoid problem all switch inputs are also tested before the boards are sent out.
