Mapping <mapping name> contains a dependency that points to a non existent port. The mapping is assumed to be invalid.
You started a session that uses a mapplet, and information about the mapping is inconsistent in the repository.
Open the mapping in the Designer, validate the mapping and save it again. If the problem persists, the inconsistency is in the mapplet used by the mapping. Open the mapplet, validate, and save it. Then validate and save the mapping again.