Tremolo playback is incorrect in MuseSounds strings

Issue type

General playback bug

Description with steps to reproduce

1. Open the attached file (incorrect sting tremolo.mscz)
2. Select one of the staves (for example, Violins)
3. The single note (B only) through-stem tremolos play correctly regardless of tempo.
4. When there is a chord (in this case G and B) the through-stem tremolo starts alternative between pitches.
5. As the tempo slows down the alternative effect becomes very noticeable.
6. The Violas, Violoncellos, and Contrabass have the same behavior.

Related question:
Does MS support selection of measured vs. unmeasured tremolos? If yes, what is default? If above playback is measured, it still should not alternate between pitches.

Tested on latest MuseScore 4.6.3 and recent nightly build also shows problem (4.6.4.253300408)
Using MuseSounds Strings (section), MuseSampler version is 0.103.2.861

I didn't see this specific issue logged in the open issues.

Supporting files, videos and screenshots

Incorect string tremolo.zip

In which versions of MuseScore Studio is this issue present?

OS: Windows 11 Version 25H2 or later, Arch.: x86_64, MuseScore Studio version (64-bit): 4.6.4-253300408, revision: github-musescore-musescore-7e32f16

Regression

I was unable to check

Operating system

Edition Windows 11 Home Version 25H2 Installed on ‎10/‎26/‎2025 OS build 26200.7171 Experience Windows Feature Experience Pack 1000.26100.265.0

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