Hi dtgphoto.
Just curious why you say it is out, how have you tested it? Not suggesting you must be wrong, but methodology is important.
I have one of those flash shoe 2way spirit levels, piece of junk, checked it with an engineers level, it was miles out! Much worse than using my judgement!
As for resetting it, no knowledge, just a thought, a reset and initial power on with the camera on a level surface?
Cheers, Graham.