ÖÄ/öä letters glitches out after playing for while

[32JP]

What happened
After playing for while(varies on the area, sometimes it takes longer, sometimes not) letters ÖÄ and öä glitches out to transplant or black tiles, hard reset and reloading save fixes this.

Expected behavior
Them not to glitch out

Screenshots
Before reset:
https://imgur.com/4Zh74Rd
After reset:
https://imgur.com/cjs0eKM
(yes I am playing on shitty composite cables for maximum comfyness)

Version
"doukutsu-fi-202310192115" - Finnish build.

Environment
Happens on both Fusion 3.64 emulators in ntsc60hz and on PAL megadrive II (playing on chinese everdrive clone), playing in PAL50hz.