Initially when I bought this cart, everything was working fine. I'd played nearly every ROM on this cart with no issues. However, I ran into some audio issues with Shinsetsu Samurai Spirits for the NGCD. I had an image that was using MP3s, and after realizing that there were known issues, I changed all of my NGCD images to standard disc images. I had my region setting set to USA, and I have a Japanese 3-6 with the stock BIOS. Any of the NGCD games I tried to load would then crash or reboot my system.
Then it got weirder.
I deleted all of my BUP files. Forced a firmware flash, and removed all of the NGCD folders/.neo files from the SD card.
Now whenever I try to load a larger ROM like Metal Slug 3 or any of the KOF games with the region option set to anything other than BIOS, the cart crashes or gives me strange graphical issues.
Older smaller ROMs like Magician Lord or Crossed Swords work perfectly fine with the region option changed.
It seems like a bad NGCD rip or image has flashed or damaged the FPGA that controls the region. I sadly don't have a UniBIOS chip installed or this probably wouldn't be an issue.
Again, I've already flashed the firmware, so that doesn't seem to help. I have a feeling that whatever FPGA chip controls the region either needs to be fully re-flashed, or it got physically damaged somehow.