root task can be moved, replaced by Unknown Task which can't be edited

What i did:

Create root task A, with subtask B, both Project type of category List. Clicked on the Down arrow on task A and it moves below subtask B. Subtask B is now attached to an entry that says "Unknown Task". This Unknown Task can't be selected or edited, and task A can't be moved back into it's original spot. Subtask B also can't be moved; it's stuck with being attached to this Unknown Task.

Delete Subtask B; Unknown Task then goes away and everything seems to go back to normal. However upon creation of another task, Project type of category List, it shows up again as a subtask to an uneditable Unknown Task.

Delete everything and restart, and things are back to normal.