Key signature change in multistave works invisible, acting oddly.

If I report an issue that's rather difficult to find the ultimate cause of, and in the course of debugging, find another, related way to crash the program, do I report that separately?

Like I have the thing with ruined save files, but I don't know how to reproduce without a large score, so I really need a debugger. But I don't know how to deal with Musescore in jGrasp or Notepad++ or whatever, so I've been trying to reproduce smaller.

I have at least the first step. The score has to be multistave, you need to add enough notes to make a system in addition to whatever you have, and then if you add in a key change - any key change whatsoever, anywhere - there is no visible key change, but every note that is supposed to be affect changes to natural.

For example, here when I add a G maj key change:

All the Fs set to natural, except for the two at the end that I probably have another key change for that I can't see.

Upon reloading the save, there is no visible difference at all where key sigs should be, and all accidentals have magically disappeared.