Saving score with VST instruments assigned destroys scores

• Mar 30, 2023 - 01:00

I have not found this in the forums, but apologies if this is a dupe.

when assigning an external vst instrument and saving the saved score becomes unusable and unrecoverable.
(External VST, not musesounds or MS basic)

Observed behavior
When re-opening a file saved while a VST is assigned as an instrument, the mixer interface is buggy.
- Where it would normally show sound and fx boxes with drop-down menus there is only one box for one or more of the channels in the mixer.
- if you try to open the drop-down menu MuseScore crashes
- if you try to play the score musescore crashes
- if you try to close musescore, musescore hangs and has to be killed through the task manager.
- You can no longer use the saved score.

if a score has had vsts assigned and played back and then subsequently the channels have been assigned back to e.g. ms basic and then saved, then, the score is still 'infected' with the VST information;
the score will open, edit and playback as usual, but if the sound drop-down menu in the mixer is touched, musescore hangs and must be killed through the task manager.

expected behavior
handle the vsts and playback in the same way as when the vst has just been freshly assigned (it actually works great, except for this save bug)
or, handle the vsts being assigned gracefully and don't play back until the channels have been reassigned to a vst, ms basic or musesounds instrument
or, show an error that the "vst connection is not working" and allow for the instrument to be changed
or, (as a workaround) when saving, check if vst is assigned and change assignment to ms basic so the file does not become "corrupted" with vst.

my system
Apple MacBook M2 Pro (i believe this problem also existed on my intel-based old MacBook, but I can no longer test this)
Mac Os Ventura 13.2.1
Musescore 4.0.2 (this has been present since 4.0 IIRC)
VST used in the attached file: XLN Audio addictive keys (but others e.g. Kontakt 7 also have the same issues)

Attached examples
score before saving with VST and the same score with the only change being a VST assigned to top voice, channel 1

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