Using mGBA build 7175-0313fedf1 on Linux (Ubuntu 21.10).
After saving and loading a savestate in Wizardry Gaiden III: Yami no Seiten, the game will be rendered unplayable in a seemingly random way.

Often it just freezes after the load. Other times it covers the screen in garbage pixels as it freezes, other times it keeps playing but the graphics are garbled and game has warped into an entirely different menu, other times it goes through several text boxes on the screen as if the player is in a battle before hanging. A couple times loading a savestate in the main town menu seemed fine outside showing a garbage text box, but checking further showed a party member had been deleted. One time the game reset itself and played at normal, except all the graphics were glitched.

I made sure the ROM had the correct hashes. I also checked if there wasn't some issue from changing things on my computer recently, and so build the current version of mGBA (version listed up top) but the issue was the same as the previous version I build a couple months ago. I checked some random other games from GB, GBC, and GBA but they all worked as expected. I can't easily test this on other computers, but I did download the Windows exe (mGBA-0.9.3-win64.7z) and ran it through Wine, and I found the same behavior in Wizardry Gaiden III while other games seemed to work fine.

I don't know how to make a debug report, but I turned logs on and found that after loading a state the logs would usually fill will multiple of the following
[STUB] GB MBC: MBC1 unknown value [random value]
Sometimes the following would appear.
[STUB] GB I/O: Reading from unknown register FF0
Some example logs.
logs.txt
Some example pictures of how it sometimes looks after loading state.