Fairphone 5 Dark Mode

The display colour changes slightly when typing in dark mode.
Does anyone else have similar problems?

When typing, e.g. in the Threema app, the black tone of the background keeps changing slightly.
The same thing happens in the browser or in the task app.

It seems to be due to the 90Hz setting. When I turn it off, there are no fluctuations in the lighting or colour.

@ iodé: Is this a known bug that will be fixed?