I just updated my iPhone from iOS 9 to iOS 11.2.1 and ever since the brightness keeps going up and down! Sometimes it'll go super bright then a second later very dull then back up again a few more seconds later and it's driving me insane! I checked and I've definitely not got auto brightness on so how can I fix it cos at times I can barely see my screen. I keep it at the highest brightness possible and when it changes itself it still stays looking like it's at the highest brightness if that makes sense
Read more: Auto brightness is off on my iPhone yet the brightness keeps changing dramatically on its own very regularly!