Thanks a lot for your hint, @Rokcy98 ! After the latest update, I had the same issue on my Zenfone 9 - the cause seems to be the same as on the Zenfone 8.
In my case, it was not the "night light" but the "dark theme" that was set to automatically "turn on from sunset to sunrise". I disabled the automatic switch and set a custom schedule for it. For now, the issue seems to be gone.