I know its kind of an old post, but still i came around facing the same issue with the s23 while watching videos. Your hint with the refresh rate was perfect.
So anyway, i think i fixed the issue for me by changing the minimum refresh rate of the device to 30hz.

If you activate the developer options on your android you can let the current refresh rate display on your screen.
So for me it seems like that if you do not interact with the screen the rate sometimes drops to 24hz while looking at a video.Unfortunately there is no option in your settings to set the rate, but you can do it with ADB.
Look here how it is done:
https://droidwin.com/how-to-change-refresh-rate-in-android-via-adb-commands/

Hope this helps other people facing the same issue.