You’re a bit finicky but you’re right 😀
It is a workaround, but in my opinion really worth sharing.
This issue stopped me from playing this game for almost three years.
The UltraHDMI doesn’t like those resolution switches. According to the posts on assemblergames, there are plenty of artefacts when the resolution switches.
1) Use a CRT
2) Use your flatscreen internal upscaler
3) Get an OSSC and a cheating device