Fretboard diagrams and exported (music)XML

When creating fretboard diagrams, the fretted notes also (incorrectly) show the 'open string' symbol above them.
When exported into an XML file, and reimporting that into another file, the fretboard diagrams are empty of fretted notes.

OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 3.4.1.9660, revision: 20414b2