Is your solenoid driver board new too? Maybe could be an issue with the 5v regulator on it if it's an original board

He means to reseat the ICs by taking them out with an extractor and putting them back in the socket. When you push down on them, put some support behind the board so it doesnt flex.

But new solenoid driver board... Im fresh out of ideas. Seems like it has to be a wiring problem somewhere. Maybe check the main AC cabinet wiring and see if anything jumps out at you, then I would start repinning all the connectors that haven't been repinned yet that deal with the 5v supply

Maybe contact barakandl and see if you can send the MPU to him for bench testing

In your collection it says you have an Eight Ball. Could try taking the MPU in the Mata Hari and testing it in there. Don't forget to change the dip switches on the MPU when swapping games

You'd have to test the aftermarket one in the Eight Ball unless you want to burn Mata Hari ROMs for your original MPU and do the test that way. I would go through and systematically swap all 3 boards, see if the problem changes or follows

I definitely would have never suspected that. It's normal for some mounting screws to be missing and it almost never affects anything. These new boards are (in theory) designed better than the originals so if one corner of the board isn't fully grounded it shouldn't be an issue. I would expect that kind of a grounding issue to happen on something like a Gottlieb System 80 or the Bally SDBs where they dont tie all the grounds together, so if one corner of the board isn't screwed in all the way not all the board would be grounded.. Glad you got it fixed regardless.