It would seem they've not fixed this problem. I'm still having the intermittent orientation lock problem after upgrading to iOS 9, and also today to iOS 9.0.1
So far, it seems to have fixed my problem with orientation lock. I play a lot of Boom Beach, which only plays in landscape mode. Since upgrading to iOS 9, I don't have to toggle orientation lock on & off, anymore.
It was annoying, but not justifiable enough to reload.
I don't think Apple has even addressed the problem, as an internet search came up zilch.
Good luck with your problem.
It would seem they've not fixed this problem. I'm still having the intermittent orientation lock problem after upgrading to iOS 9, and also today to iOS 9.0.1