I do have similar issues on auto brightness too. It tends to become quite dark when I am on the MRT, and become too bright when in the dark, I had to manual adjust a few times per day. Not sure is it because I just had the phone for a few days so it is still sort of "learning" now.No issue here.
Don’t turn it off. It only resets the calibration. You train it by adjusting it to whatever brightness in different ambient brightness.
Also are you using a screen protector that covers the sensor suite on the display?
I am using Spigen full screen protector (black border), not sure does it block the sensor suite though.
