I'll take a guess and think that the Home menu got corrupted, so I'd try to replace that. You're in Godmode9 so you can hardly screw up. I tried looking up your problem and didn't find anything either.
Seems like It's not your easy sit-in-the-afternoon project sadly, but @FAST6191 did cover this GBA article which could help you out.
https://gbatemp.net/threads/gbatemp-rom-hacking-documentation-project-new-2016-edition-out.73394/
We had a lot of cases regarding emulation and legality. I can also use Yuzu (among any other emulator) to play my legally owned games at higher framerates or higher resolution.
Is anyone familiar with former forum opg.life ? I missed the transition to the new forum over the week end (was scuba diving in the sticks with no internet connection). If anyone in touch with any members please pm me.