Cannot add multi-measure repeat while on multi-measure repeat

Issue type

File corruption

Description with steps to reproduce

(I chose issue type "File corruption" as that seems to be the most severe applicable issue type. "UI bug" would also apply, and I believe I have also encountered a crash while playing around with this, though I have not been able to reproduce that so far.)

1. Create a score and some music, making sure to leave a couple of empty measures at the end
2. Switch to a part score (this causes multi-measure rests to be enabled by default)
3. Click on the multi-measure rest
4. Upon creating measure repeats from here, two problems arise...

Inability to create multi-measure repeat while on multi-measure rest

If you dare try to create a multi-measure repeat, you'll get an error with the message "Insufficient or unequal measures"

I would expect this to instead create a single multi-measure repeat at the start of the rest. (and perhaps focusing any remaining rest, so another multi-measure repeat could be added quickly?)

Corruption when undoing creation of single-measure repeat

If the user instead chooses to repeat a single measure, it seems to work fine at first and even allows users to "upgrade" the "repeat one measure" to "repeat 2 measures".
This, however, completely breaks if reverting the changes with Ctrl+Z: While the measure appears normal on the part score, the full measure of rest is missing if switching to the main score, leaving a broken and corrupted measure.

After clicking around some more in the score, the measure is also highlighted in red, indicating that the program recognizes there is something wrong with the measure:

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/e850dd23-f240-4fcd-a324-a36998b7270c

Score download

You can download the scores (before and after the corruption) here (remove the .zip to open):

• mscore_repeat_bug.mscz.zip
• mscore_repeat_bug_broken.mscz.zip

In which versions of MuseScore Studio is this issue present?

(Please convert this to a multi-line field in the issue template, I had to edit it afterwards. Behavio(u)r across different versions can be complicated and may require more space in an issue)

• 3.6.2: Corruption on undo reproduces, multi-measure repeats seemingly didn't exist yet
• 4.0.0: The corruption on undo does not seem to occur?? Creating multi-measure repeats fails
  – 4.6.5 (latest release at the time of writing): Both problems reproduce
• Latest nightly: Could not check, as I was unable to enter note input mode for some reason

Regression

No. It's complicated, see information on versions above.

Operating system

Arch Linux

Additional context

No response

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible