Unfortunately this is a bug with mkxp-z, which I don't manage. This is on the issues page for their github, I just don't know when they will fix it.Bug: Occurs when walking into specific areas. Similar issues occur when certain fights start View attachment 4770668
Important note: This bug does not occur when launching with Wine. Wine does run a lot slower though, so I prefer the launcher you created.
It has something to do with having Japanese characters in the image file names, I think macos treats them differently from windows.