Linked staves become not linked if part is removed
1) Create a new score, e. g. treble clef template.
2) Go to Instruments, add a linked staff.
3) File→Parts→New All→OK
4) File→Parts, remove the created part, OK.
5) Try to input some notes to the first staff.
Result: notes do not appear in the second staff, and measures in it just get empty. Saving at this state produces a corrupted file.
Fortunately, it is at least undoable: after undoing to the moment when the part was present or right before that all seems to work well.