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I believe it's a software issue on the device itself. Used to happen all the time on my case less Air 2, but since I got my new 12.9 it's been fine.

I hadn't seen it in some time but now since the 10.2.1 update it has happened twice in 24 hours.
 
iOS 10.2.1 STILL doesn't fix this issue . When this issue will be fixed anyway?
I think 10.2.1 made it worse. This was a very seldom glitch that didn't really bother me because it so rarely happened. I just updated today and the orientation has locked up twice on my iPad Air 2 requiring a reboot.

Not happy.
 
I had this issue as well on my iPad Air 2. It got materially worse with the last update (10.2.1) that I couldn't get it to work again without resetting the device (power plus home button). In a last desperate attempt, I did a complete factory reset (without restoring from backup) and it's finally working fine again.

Your mileage may vary..
 
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