[SOLVED] Reference is out of search scope?!

I have a concept A and a concept that references A: AReference. Inside the reference concept, I want to define the scope in the Constraint aspect. Everything is in the same model! So I use the SimpleRoleScope or even the ModelPlusImportedScope to get the concepts of A into my scope. Completion/Substitution menu shows the right entries of instances of A to be chosen as reference. However, MPS says that the Error: reference is out of search scope?

Any ideas why this could be the case?

Cheers,

Dennis