Fretboard diagrams: barré deleted when you add a dot at another position

OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 3.0.3.5341, revision: e06ea8e

If you create a barre or partial barré, it will be deleted if you add a finger dot anywhere in the diagram. e.g.

1. Create a partial barré (A6 chord) by Shift + clicking on the 4th string, 2nd fret:
   
2. Click on any other position in the diagram, e.g. 1st string, 3rd fret (A7 chord)

Expected result: The barré stays in position:

Actual result: The barré is deleted:

Related to #283681: [EPIC] Fretboard diagram issues.