I finally broke down and bought some new ROMs from Matt Osborn. Replacing them brought up a nearly working game. Just some graphics glitches.
I went to town with it today, touched up every solder joint on the A/R II and a bunch on the main board.
Surprise! No more graphics glitches. I figured it had to be something like this because you could slap the side and the screen would change. Not anymore.
New issue: the archer now moves on his own. I remember seeing something like this on a repair log. I’ll have to dig it up.
And I still get a ROM 4 error. Likely due to a missing voltage. I’ve ordered some parts I think will take care of that. It’s a pretty simple circuit. Instead of troubleshooting it, I’m just going to shotgun it.