Margin labels for shared staves unexpectedly be affected by system breaks

[davidstephengrant]

Issue type

Engraving bug (incorrect score rendering)

Description with steps to reproduce

In the attached video, the label for Horns on system 1 should be "Horn in F 1-4", not following the voice assignment for the next system. This corrects itself if an explicit system break is added at the end of the first system.

Supporting files, videos and screenshots

Screencast.from.2026-07-02.12-29-23.webm

In which versions of MuseScore Studio is this issue present?

In #34036

Regression

No.

Operating system

Ubuntu 24.04.4 LTS

Additional context

No response

Checklist

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• 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