I’ve only seen this after having clicked on a folder in the binder so that I see all its contents in the editing panel with separation lines between them, as shown in the first screen shots (top, side-by-side).
What happens is I’ll start typing in one of the folder’s documents and, for no reason I can see, the cursor leaps up to the folder’s first line (Heading 1 in this case) and the typing continues there, as shown in the third screen shot.
(note: No carriage return, just a space and then “I’ve been…” It just so happened that all but the space line-wrapped.)
I haven’t noticed any pattern other than what I described above, so I don’t know exactly when it’s going to happen or what the trigger is, but it invariably happens after typing a bit given the same set up.
I don’t have any similar problems when I’ve selected a single document to edit.