Thanks for including the model of the console. Those are actually clone consoles, so it is likely the implementation of the Z-80 and Audio ASIC in the GOAC. The developer will be able fix it knowing that.
Viewing post in TMNT: Arcade Game - Megadrive Port comments
My Mega Drive 3 from the Brazilian company TecToy is actually the model 2 in the rest of the world. It's an official video game console from the early 90s, and it has a Sega CD slot. Here are some parameters of this console that I forgot to include:
M68HC000FN8 (CPU)
Sega 315-5660 FC1004 (GOAC)
Sega 315-5676 (Z80 clone)
That is good to know. By the way, the Sega 315-5660 FC1004 is an integrated ASIC. The Sega Genesis Model 2 VA0 has its own issue in that if the expansion bus is not terminated by either a 32x dongle or a Sega CD, the newer Everdrives sometimes throw weird errors. Especially the Mega Ever Drive pro.
The full GOAC is when all of the parts are on the same dye. In the USA, the Sega Genesis Model 2 VA4 and the Sega Genesis Model 3 VA1 & Sega Genesis Model 3 VA2 have a full GOAC, with the Sega Genesis Model 3 VA2 being the most problematic as it has many Z-80 signals eliminated. I've found ALL of the versions with the GOAC are have problems with homebrew.