Boktai 2 desyncs

[RetroEdit]

It's a bit unclear at the moment whether the Boktai 2 desync is from BizHawk or mGBA, but I figured I'd make an issue here since I have some reproduction steps for observing the desync in BizHawk.

See also: mgba-emu/mgba#3294

Repro

Thanks to some help from Drakodan, I was able to find a simple situation where it desyncs.

These are for BizHawk 2.10-rc1 and this version:

Zoku Bokura no Taiyou - Taiyou Shounen Django (Japan)
SHA1:54A4DCDECA2EE9A22559EB104B88586386639097
MD5:F4E3DEAD5AF182598623CF89F9A428F4

1. Load the game
2. Open up virtual pad and set light sensor to 220
3. Load this savestate: Boktai2_frame_23305.zip
4. Frame advance twice to reach frame 23307. Observe the sun meter at the bottom is grey.
5. Continue to frame advance until you reach frame 23331.
   5a. If you stop earlier, it probably still has inconsistent state internally, but it won't be as blatantly obvious.
6. Load the savestate from step 3.
7. Frame advance twice to reach frame 23307. Observe the sun meter at the bottom is orange, inconsistent with step 4.

There's also this movie from Drakodan that goes through the intro and was truncated at 23345 frames; I originally used this movie to find a spot where the light sensor was used and then stopped TAStudio to create the savestate: Boktai2_desync_test.zip