Check for bad connection for the comma signal from the CPU to the display board.

Those pin numbers are for the glass itself.
You need to trace the wire from the CPU board to the display board.
Actual connectors, pin numbers depend on which game this is for but typical would be CPU J22, pin 26 to display J3, pin 26.
Are you using original ribbon cables? Could be a bad ribbon cable.

To narrow this down further - need to rule out which board is causing the issue.

The CPU board provides a "DOT" and "COM" signal to the alphanumeric displays.
The DOT = the dot portion of comma, the COM = tail portion of Comma.
As shown in first photo - the tail is lit but the dot is not.
The problem can be at the CPU end or the display end (or could still a bad cable).

Check the CPU board to make sure both DOT and COM are being driven equally.
For starters - check voltage reading at pin 9 of U41 to pin 17 of U41. Best method would be to use a scope to compare both simultaneously but a voltage reading *might* give us a clue.

And as wdennie mentioned - post a photo of the U41 section of the CPU board. That's right in line with the batteries and the mentioned COM and DOT signals pass right under them on it's way to J22.

Looks like there was a bit of corrosion on B2 at the negative end (???). Normally see corrosion at positive end so could be something else. U41 does look clean of corrosion.
Need pix of the SIP resistor/capacitor networks and connector J22 just above the battery holders in photo 1.
If ok -- you'll need to start scoping things out to see where the signal is stopping at.

Yep - you're to that point. Follow the signal from beginning to end and see where it stops (or if it is stuck).