(dev builds) mGBA can't load savestates from any original Game Boy game

[RafaelTrepaUnCarballo]

UPDATE: The savestates of all original Game Boy games are broken in the latest x64 dev build, or at least all the .GB roms I have:
Avenging Spirit, Donkey Kong Land, Final Fantasy Adventure, Kaeru no Tame ni Kane wa Naru, Kid Icarus - Of Myths and Monsters, Kirby's Dream Land 2, Mario Land (unless I autoapply the GBC color patch).

GBC and GBA games still works fines, though.

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OLD: The latest dev build is unable to load savestates in Popeye 2. The savestates were made seconds ago with the same build.

I tested mGBA-build-2021-03-05-win64-6807-cc739bb369b981ba1a053417bd5a1e4c981e7bfb and another build from weeks ago (I forgot which version), both suffer the same bug.
The stable 0.8.4 has no problems with that.

I noticed the log of the dev builds gets filled with this game error:
[GAME ERROR] GB MBC: Attempting to switch to an invalid RAM bank: 0

When I try to load a save state this appears in the logs:

[WARN] GB Savestate:	Incompatible savestate, please restart with correct BIOS in DMG mode
[INFO] Status:	State 1 failed to load

I'm using Windows 10 x64 with the x64 build.

[endrift]

Are you using a GBC BIOS for GB games, e.g. to get colorization?

[RafaelTrepaUnCarballo]

No, I didn't use BIOS files.

After more testing I noticed:
-The bug only happens when emulating the DMG and SGB models, but if you use GBC or GBA it works fine. (no bios needed)
-Using the GB Bios also fixes the bug
-In DMG model, without the BIOS, you can load a savestate made with BIOS and from that point you can create new savestates and load them without a problem.

[endrift]

Thanks for the report. Unfortunately the old savestates recorded an erroneous value which is why they're refusing to load. These savestates will not load unless they are manually repaired.