I've come across a number of issues with the gameboy/gbcolor machines that only repro on my RPi4 (currently Debian 10.12, 64-bit beta OS). The bugs also repro both with self-compiled top of tree (0.245 at freeze) and the Debian 0.206 package. As an example here's a screen shot from riddickb:https://imgur.com/a/tT2zbPB.png
In MAME on macOS (at least) two boxers appear in the ring and the game is playable. Note also the overhead view at the top has one of the little boxer sprites shifted way down to the main ring. Furthermore, the game is not totally frozen, as 'start' will bring up the in-game menu to quit and you can return to the title screen that way. Anybody else with a Pi see this behavior?