Yes of course. Thanks!!!
I solved the same issue month ago and it also took me hours to figure that out. Got off track with the cast note. I just forgot to choose the Default value (BP_Rotator) for “0_Base” character in the details panel. This is such an annoying Engine implementation and not intuitive whatsoever!
Here the tutorial for everyone else: Direct Blueprint Communications | Unreal Engine Documentation
This only works if I drag my character into the scene because only than I have the details panel. How can I do the same if I work with "PlayerStart"s? In this case I can’t set the default value.