Hi Jeroni!

This fade looks so nice it seems a feature instead of a fault. Have
you checked all menu options to ensure some weird option has not been
enabled?
So maybe I should sell this monitor for it has this extremely rare,
special feature? Nope, unfortunately, there are no menu options
like that...

It could be some weak voltage from
the power supply, probably a bad capacitor.
OK, thanks for the hint. That model is known for having problems with
capacitors, but commonly described symptoms are different from what I
observe. I'm going to change the capacitors, anyway, and keep you
posted.

Thomas