An AssociationGroup can contain only one {0}. AssociationGroup '{1}' on Entity (External Content Type) '{3}' with Namespace ...

An AssociationGroup can contain only one {0}. AssociationGroup '{1}' on Entity (External Content Type) '{3}' with Namespace '{2}' has a reference to Association '{4}' on Entity '{6}' with Namespace '{5}', which would be the second {0} in the AssociationGroup.