Nice job there mate
You've given me the idea to disconnect CN8 and CN9 then do the short for TP19/20 which will avoid stuck switches and shorted diodes from the game.Regarding the programming issues, if there is no response to the TP19/20 short (normally get a warble) check Row1 (grey) and Col0 (Grey/White) for any stuck switches or shorted diodes. The lack of change on ROM1 CS sounds very suspicious though! If you need any help with ROMs let me know.
That will certainly eliminate any issues caused by the game wiring and switches. Note that ROM1 is the boot ROM and is the same code and checksum for all of the Gen1 games with a 2716 in position 1, whcih can be useful if you have another Gen1 game to borrow a ROM from (or test the ROM in).You've given me the idea to disconnect CN8 and CN9 then do the short for TP19/20 which will avoid stuck switches and shorted diodes from the game.
Yes, it is suspicious. I couldn't decide if it's stuck on ROM1 until it has received programming. The activity on the data lines (DS3) may be a symptom or a cause.