MIDI loop - Note inputs forever when switching to MS Basic sounds

Issue type

UX/Interaction bug (incorrect behaviour)

Description with steps to reproduce

1. Create a score with any instrument
2. Open the mixer and change the sound from Muse Sounds to MS Basic
3. Try to input a note

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/17ba8ce8-3449-4686-a7c6-9f818953583e

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

4.5.1-250800846, revision: github-musescore-musescore-603eca8

Regression

Yes, this used to work in a previous version of MuseScore 4.x

Operating system

macOS 12.7, Arch.: x86_64

Additional context

If you change an instrument to MS Basic sounds then if you try to input a note it keeps inputting it on loop forever and the only way to get it to stop is to close the program, but it never sends a MIDI note off message so the note keeps playing after the program is closed. I had to open a Logic Pro project and hit the play button which sends that message to get it to stop playing.

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

No source files, tests, or code entry points are named. Reproduce the loop using MuseScore Studio 4.5.1 on macOS 12.7 by switching from Muse Sounds to MS Basic and entering a note, then trace the MIDI note-input and sound-switching paths. Done means note entry produces one note, sends note-off correctly, and stopping or closing the program does not leave a note sounding.