Bug when moving low notes (score editor)

C15pro.
Trying to move a low note makes it jump to a random place:

works as expected with a higher note:


But why does that slur appear?

It’s easier to do it in the key editor. The score will reflect the actions you take in the key editor.

sure, that´s one workaround of some more I can think of - but it´s a simple edit, that should work in the score editor, too.
Selecting the relevant part in project window, opening a different editor, doing the edit, selcting the parts I had displayed in the score editor again - those are way to may steps for moving or copying (which leads to similiar random results) a note.