Uh...
So, I found something wrong with both cores of GBA for BizHawk 1.11.3 and 1.11.4
Steps:
1. Start Monster House,GBA
2. Open this ram watch
Domain EWRAM
SystemID GBA
00F9D8 d 3 0 EWRAM
00F9DC d 3 0 EWRAM
02E3EC d u 0 EWRAM
02E534 d u 0 EWRAM
02E78C d u 0 EWRAM
02E790 d u 0 EWRAM
02FF04 d u 0 EWRAM
02F49C d u 0 EWRAM Basement 1
02F4C4 d u 0 EWRAM Basement 1
02F740 d u 0 EWRAM Basement 1
02FD88 d u 0 EWRAM Basement 1
02FDE8 d u 0 EWRAM Basement 1
02FF48 d u 0 EWRAM Basement 1
02E1E8 d u 0 EWRAM Floor 1
02E354 d u 0 EWRAM Floor 1
02E454 d u 0 EWRAM Floor 1
02E4BC d u 0 EWRAM Floor 1
02E4F8 d u 0 EWRAM Floor 1
02E560 d u 0 EWRAM Floor 1
02E5D8 d u 0 EWRAM Floor 1
02E630 d u 0 EWRAM Floor 1
02EC30 d u 0 EWRAM Floor 1
02EF20 d u 0 EWRAM Floor 1
02EF5C d u 0 EWRAM Floor 1
02F050 d u 0 EWRAM Floor 1
02F120 d u 0 EWRAM Floor 1
02BFB8 d u 0 EWRAM Floor 2
02E2C4 d u 0 EWRAM Floor 2
02E580 d u 0 EWRAM Floor 2
3. Find out which value corresponds to the correct one.
4. Right click and select "View in Hex Editor"
5. Slightly before it should display a value saying "B841B944" or something similar. Zero it out.
6. Move around a bit
Now depending on the core, the following will happen:
VBA next: Emulator crashes
MGBA: Game crashes, and savestates become "glitched"; loading other savestates won't fix the crash.
Here's a video of the "savestates error"
https://youtu.be/g04PqDbmDPU
Also, completely unrelated, but sometimes the change counter in the RAM watch advances even if I paused emulation.