Dragging note horizontally removes accidental permanently

MuseScore r3990 trunk and branch

1. Create a score in C major
2. Add a C sharp
3. With your mouse, drag the notehead of the C# horizontally and release

Expected result : Nothing should happen
Actual result : the # is gone. If you move notehead with up/down arrows the sharp (or any accidental) is not drawn. A look in the object inspector and you can see that the accidental is still there. It looks like a draw problem since the ledger line is reduce and layout phase made some room for the accidental.