Thank your for your advise. But I think I found out what it is all about:
It looks that the Moog has a bug when using the following configuration:
I use Main L/R out for single use of Synth 1
Sub L/R is chosen for Synth 2 and 3 (unfortunately the is no 3rd output seperatly for synth 3)
In the output area I mention that Main-Synth 1 is ON and Main-Synth 2 and Main-Synth3 is OFF
Sub-Synth 1 is off, Sub-Synth 2 and Sub-Synth 3 is on.
The Inserts are all OFF
All “kocal-off” functions (keyboard control) are OFF !
Now pay attention:
if I play now one synth after another while selecting and arming a different channel in Ableton everything works fine 
But if I (by accident) aktivivate another synths local off and after that all three continue to be active.
Deactivation the last step let it stay the same.
This happens not every time but if so I have to deactivate in the output area the Main-Synth 1 for a second and after enabling it it works fine again.
Really strange behavior bat thant the reason why I had this problems to play only one,- the chosen synth.
Thank everyone for take part in the discussion, I think together we can find out more then only google search can do
regards
martin