RobotStudio event

ArcWelding Instruktions in second Positioner Task

Hey Everyone,
I have a Robotstudio System with 2 Robots and 2 Positioners in a MultiMove System.
I had to add the second Positioner with the external axis wizard. Everything is working fine. The two positioners are controlled by axis 7 and 8.
The problem I have is, that I am not able to use ArcMove instructions in the Task of the second positioner. All other Task (Rob1 Rob2 and Positioner1) are able to run ArcMove instructions. By writing an ArcMove Instruction it is red unterlined.

Has anyone a hint how to add the Arc functionality also to my second Positioner Task?
Tanks

Daniel