I found some very strange thing to explain
I mad one scene that fade in and out only the Colors of LED spots
in my example only red and the green and blue ones stand at "on" but 0
and the dimmer stand at "off"
when I go to the Live screen and use the dimmer only one time and then start the scene - the dimmer will ever got to 0, when the scene stop the dimmer went back.
When I go back to the edit mode, the dimmer fader in my scene stand at "on"
I think that is strange