Are these original Bally 7-digit displays? The credit/match display should be a 6-digit. What if the score is under 100K, are the commas still lit?
The commas are driven passively by a simple logic circuit on the display board. There would have to be a short on the 7 digit enable wire to allow all the commas to light when there is no data. Look for a short or misswire.

The commas light when there is data for the 4th and 7th digits. It's happening on all the displays even if no data is present. That should not happen.
Have to believe there is a short that puts noise out on the digit enables. I would start with one known good display If that has flickering commas even when at 0, I would first swap U10 and 11 on the MPU if original (disregard if Altec). Next I would pull all 7 digit enable lines from the connector. Then I would reseat them one at a time from 7 to 1 in that order. That would tell me if there is a short on the enable line.

Possible a lighting short took out the PIA chip or there is a short to one of the digit enable wires.

Sounds like something fried. Try replacing the diodes and drive transistor for the commas. Also, measure the 190v. perhaps it's too low and affecting the commas.