I think I've seen this in the US version too. Not sure why it's inconsistent though; every time I've tried to debug it it doesn't happen.

Which OS are you trying to get it to break on?
I could set up a quick VM with that and see if I can reproduce it there to maybe rule out OpenGL on Windows as the issue (unless it's *BSD which will leave me begging for mercy :) ).

Also, if you can reproduce it, a savestate of when it's in the broken state might be somewhat helpful? At least it would confirm whether the issue is PC-specific or an actual emulation problem.

While trying to reproduce I have noticed something curious. I had continued playing on my save since opening the issue and couldn't reproduce the error anymore.
I could however reproduce again on a fresh savefile, while only having Mario as part of my team, Luigi is only still hanging around, not part of the actual battling team. As soon as Luigi joins, I cannot reproduce any more.

While messing around I even found another bug occuring on the save screen only.
When I enter the "Mario Bros." mode on the start screen, exit out and then enter "Mario & Luigi" mode, it looks like the save game's behind prison bars. This bug I can reproduce consistently at any game state.

You can find savestates of all that attached.

• ss1 for a state working just fine
• ss2 for a state with the broken graphics of the original bug description
• ss3 for a state of prison cell mode

mlss-states.zip

is that "mode" only in the OpenGL renderer too?

Seems like it, couldn't force it to happen on Software Renderer at all.

Ok, I'll try to look into this tonight. Thanks for the savestates.