Expert LCD Brightness Max = Sounds Best?

[Vivialet]

yes, I know that of course. But after startup the dispays go off and stay off. As soon as music plays the on/off cycle starts. After about 20 seconds the display goes on again and off after the delay has expired. I also tried removing the wifi and ethernet config, works but no difference.
Maybe it is some other configuration difference...I'm using sweet room e.g.
For now I keep the displays always on.