What's your MPU's +5v reading? Has the PSU been recapped before? It seems unlikely a brand new 22uF cap would be faulty. I think you may be addressing a symptom here and not the cause.

Good info. The board does look clean, but you never know what is under that battery holder. You're probably okay there though on the corrosion part I'd guess.

So If I understand you correctly, you were running the game with the additional 22uF cap clipped in place for while, then took the board out to install the cap, you put the MPU back in, and it is back to the original issue? So you're not doing this on the bench, correct?

That would definitely cause the problems you are seeing in the POR circuit and possibly had something to do with the issues with your audio decoding. Did you get a reading on the test points for the 12V lines prior to taking it out of the backbox? And did your CSVD take a dump as well, or just the DAC?

I've had to replace ZR2 before in a SYS11 MPU that had similar boot issues.