I should note that I socketed the v4 and have replaced the z80 with one from a neo-geo, and then put the original back in.
Bad solder on both A+B boards is a long shot considering exactly the same issue is occuring no matter what combination I use.
I havent tried decrypted roms because the keywriting is working fine, but I have tried different SD cards and game compilations ect, always the same result with any game.
Its timing seems random, as it used to do it before SF vs Xmen could do a single attract loop, now it can take an hour or more.
Bad solder on the multi maybe, I have looked over it with eagle eyes and nothing jumps out at me.
I cleaned and reflowed all pins and connectors. If I had an oven Id bake it and see if that helps but I dont.
But a bad joint would show itself when I flex the board whilst its running but if I tap on the multi or push on areas it just wont glitch, and hasnt shown any sign of jailbars or glitched text ect.
What part of the multi would make the Qsound or z80 chip crash? or if the Qsound or z80 cannot crash whats feeding it that could crash? Where should I look for bad solder ect?