Thanks for testing! The reason I pointed this out - I tested the 1FZ again yesterday and found depending on when I applied the patch made a difference. For instance, if I wait for the music to start and you hear the narration on intro, then patch that address - I found it made no difference, but several seconds later it suddenly popped in the right channel. It then remained stereo after eitther soft or hard reset. And likewise I found if I patched it ASAP just after unibios allowed, stereo was there right away. I could repeat that every time on the 1FZ.
The guru at BB suggested perhaps the YM2610 is processing the block of ADPCM and cannot correct itself due to the fact it started with borked banking, but on some boards it seems to correct itself, perhaps as it starts the next block. There could be other things going on with the 1C, but lots of work and testing is ongoing. I am hoping to test the perma fix shortly (I just need to feel well enough first so I can concentrate on what I am doing so I dont create myself problems lol).