I finally got it to work after two weeks. Evil_Pee reminded me to surely enable every single plugin that is required for it to work - especially toggeling the Shader ‘SM6’ in the Project settings - since the editor only reminds you once. Followed by a hand full of blueprint edits: more concretely, updating calls/gets for Skeletal meshes in the Crowd_Character_BP) and it worked like a charm!