I have already tried disabling:
Ambient Light Detection
Energy Saving Mode
Still, when I am watching Netflix in a fully dark room and the show (namely, The OA) has lots of dark scenes, I can see it keeps changing the overall brightness up and down constantly. I have not really noticed it happening other times.
Any other ideas what is causing this?
I usually keep Picture Mode on Natural
It is caused by subtitles on HDR content. Once they appear the TV increases the brightness (for white subtitle text), and washes out the rest of the image.
It has been acknowledged by Samsung, but like several other big problems, nothing has been done to prevent the issue.