Rotation issues:

[Wmlaveck]

I recently updated my Nexus 9 to android 7.1.1. Now I have to reset the auto rotation once a day or more. The system keeps switching back to fixed position in settings.

 

[Tim1954]

Generally speaking, if you wipe cache partition after updates, that should freshen up your device and avoid such irritations...

 

[B. Diddy]

Welcome to Android Central! I agree with Tim1954 -- here are the steps: https://support.t-mobile.com/docs/DOC-31639