Issue with Part name / MIDI Track name

As far as I understand correctly from documentation and reactions to other issues, the Track name in a MIDI export should be set to the Part name. However, when I change the Part name, the MIDI export still has 'Piano' in the Track name.
See attached 'Test' files (where Part name is changed from Piano to Testpartij).

A secondary issue is that renaming the Part name does not survive Save/Open of the .mscz file: it is reset to Piano. To reproduce: create a new score, change the Part name, Save, Open and look at the Part name again to find it unchanged.
It is a bit of a spurious error, because sometimes the new Part name does stick. But I have not found any logic as to what to do to make it stick,
'Test1' has kept the new Part name Testpartij, 'Test2' still resets to Piano.

OS: Windows 10 Version 2009 or later, Arch.: x86_64, MuseScore version (64-bit): 4.2.1-240230937, revision: d757433