Go for a factory reset.. it will definitely help. I personally witnessed it

I sometime witness a dark black notification panel even with a light coloured wallpaper.

Battery issue can easily be taken care of with the help of factory reset.. I'm getting better battery health even as compared to UI 5.1.. I'll recommend you should definitely go for it and see the massive improvements.

If possible, a factory reset will definitely help.. but don't go for it if the issue is tolerance

Yeah it's a known issue.. they will fix it hopefully in the upcoming beta version..