Hi, thank you for the extra info.
I tested with the ROM Eliminate Down (Japan) (En).md in RetroArch using both PicoDrive and Genesis Plus GX, and I experienced no sound issues. I also tried different sound drivers in RetroArch, but the results were the same — sound worked fine.
I checked the continue screen in BlastEm with Remix mode, and the countdown appeared correctly.
I also compared Eliminate Down (Japan) (En).md against the recommended Eliminate Down (J) (REV00) [!].bin using the ROM Hasher from ROMHacking.net, and they matched. Still, I suggest patching the recommended ROM with the ROMHacking.net patcher, just in case there’s a subtle difference.
If possible, try testing on a different PC with a fresh RetroArch install and cores downloaded directly through RetroArch.
Since the hack was created with real hardware in mind and tested on a Mega Drive VA4 (along with multiple emulators), and because the hack never touched audio code, I suspect the issue may be specific to your setup or configuration.
Thanks again for taking the time to test and report — if you do find what’s causing the issue, please post it here so anyone else who runs into the same problem can benefit from the solution, and if anyone else experiences the same issue, let me know so I can investigate further.