Dear people
The riddle is solved!
Thanks to the incredibly cooperative Tangent Support, who even installed Isadora Demo to understand the case!
It was simply due to the fact that the OSC naming convention must be followed when assigning the OSC address in the Tangent Mapper.
In contrast to TouchOSC, which already “prepares” the address, the Tangent Mapper requires a “ / ” followed by the address/address variable.
Otherwise Isadora will clearly not recognize the address as such. Hexler protocol does this because it simply auto-completes the address with the missing “ / ”.
It's actually quite simple, you just have to figure it out first 😄
Now i can go straight forward by controlling PTZ cams with a colorgrading panel...
In any case, thank you very much for all the tips and your help!
Have a nice week, Tom