Crash saving project with parts

[davidstephengrant]

Issue type

Crash or freeze

Description with steps to reproduce

Saving a score with parts freezes or crashes - sometimes immediately, other times after repeated save actions.

This happens after parts have been created (regardless of whether they are currently open as tabs or not).

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First:
ERROR | 135402983773888 | TWrite::writeItemLink | ASSERT FAILED: eidOfMainElement.isValid() /home/runner/work/MuseScore/MuseScore/src/engraving/rw/write/twrite.cpp:523

Then freeze/crash.

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Once I have also seen corrupted size vs. prev_size printed to terminal, which I'm not sure if is related in any way.

INFO  | main_thread     | ActionsDispatcher::doDispatch | try call action: file-save
corrupted size vs. prev_size
/tmp/.mount_MuseScicfiHI/AppRun: line 26: 18740 Segmentation fault      "${APPDIR}/bin/mscore4portabledev" "$@"

Supporting files, videos and screenshots

Screencast.from.2026-05-21.09-54-55.webm

In which versions of MuseScore Studio is this issue present?

Nightly main

Regression

Yes, this works in the latest released version and is broken in the nightly builds

Operating system

Ubuntu 24.04.4 LTS

Additional context

No response

Checklist

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• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible