How to Downgrade From iOS 11 Beta to iOS 11 Without Factory Resetting My iPhone is really starting to act up on the iOS 11 beta and I was wondering if there is anyway to downgrade from the iOS 11 beta to the regular version of iOS 11 without having to factory reset my iPhone.
It's been a while since I did this but if I remember correctly, go to beta.apple.com on your phone and login. Go to the IOS section and un-enroll your device from the beta program. It should then allow you to download the non beta updated version of IOS 11.

It is likely the same build that you are running now. I am not sure if beta builds have extra debugging code in them or not. If this does not fix it you may need to back up the phone, erase it and restore from backup.