I have the same annoying issue here with my Xiaomi P1 TV 43". The backlight level goes to maximum after some time, and changing it in the settings doesn't change anything. The only thing that works is rebooting the TV, but it's very annoying to do it everytime. It seems to be a recurrent problem.
Does anyone with a P1 have this issue? Any workarounds?
I have a 55 inch but no back light problems