see if any of the latch strobes are shorted together. can do some resistance comparisons from the working MPU to the one acting up. If the latch strobe is happening at the wrong time the displays will read/display data intended for a different display.

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try swapping the U10/U11 PIA chips that drive the displays to see if the problem follows a PIA chip

here are a few from my chip graveyard.

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Some more.

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I used to fix a lot of bally and WMS MPU boards. Dead 5101s was pretty common. I've got a nice 6810 collection too as I would always convert 6808s to 6802s in the sake of one less socket.

So many different brands back in the late 70s to early 80s.