Odd. If you hit Tab, does it still remain stuck that way?
I tested this on my surface 3 and it is working correctly. Something is stopping it from changing. Have you tried resetting the preferences?
Yes, it does even if i press "f" twice:)
I think i I figured it out.
So problem appears when i create or open file in horizontal mode and then i turn tablet to have it vertically. The fastest way to work this around is "create new document from current state" option (used in vertical tablet position of course) Screenshot shows that rearranging windows does not works.
When i create or open file in vertical position i have normal, full sized file window.
OK, I only tested it with a blank document - But it was opened so it should have affected it if that is the issue, which would be should be bug as that is not normal.