Parts and corresponding files in `Excerpts/` are rearranged on saving

Issue type

Opening/saving issue

Description with steps to reproduce

I'm writing jazz big band charts, and saving them as uncompressed .mscx files so I can track them in Git. I'm running MuseScore 4.4.4.243461245.

When I create a jazz big band chart, the parts (and therefore the files in Excerpts/) are ordered in a sensible order - i.e. the same as in the main score: saxes 1-5, trumpets 1-4, trombones 1-4, guitar, piano, bass, drums.

However, when I close the score, re-open, and save, MuseScore will regenerate the parts in a completely different order.

This order isn't deterministic - I can close and reopen the score, and it'll give me a different order each time.

This makes finding parts in the parts tabs difficult, but also makes tracking the contents of Excerpts in git difficult, as MuseScore renames them everytime I re-open it!

In the example in the screenshot below, all I did was:

• Create a new empty big band score
• Generate parts with Parts->Open All
• Save: Parts are in the correct (i.e. main score) order
• Commit new score and parts to git
• Close MuseScore
• Re-open the file in MuseScore
• Parts order in the tab bar has changed
• Hit save - no changes were made
• Excerpts files are mysteriously re-ordered to a nonsensical order (the same as the new tab bar order)

Thanks!

Supporting files, videos and screenshots

Here's an example of how the files get renamed after saving on Mac:

What is the latest version of MuseScore Studio where this issue is present?

4.4.4.243461245

Regression

I was unable to check

Operating system

MacOS 15.2

Additional context

This is on my Mac running MacOS 15.2. I have not noticed this issue on my Linux machine but I'll double check.

This issue does affect the latest nightly (I tested MuseScore-Studio-Nightly-250670403-4.5.0-e138427.dmg)

This might be related to using uncompressed .mscx files rather than .mscz - I can't reproduce this when I save as .mscz and use unzip to check the file order. Note that I did have to manually unzip the .mscz to create the initial uncompressed project - the "Uncompressed MuseScore Folder" in the Save dialog doesn't seem to actually work for me on any platform, it always writes a .mscz regardless of whether I select it or not.

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

Reproduce the issue by creating a big-band score, generating parts with Parts->Open All, saving as uncompressed .mscx, then closing, reopening, and saving again. Trace the parts and Excerpts save path to identify why their order changes between sessions. Done means reopening and saving preserves the main-score order and avoids renaming unchanged Excerpts files.