Message Oracle LSX-00018 - invalid schema context

ERRORinvalid schema context
CAUSEAn invalid schema context was provided to the processor. Multiple schema documents were loaded and assembled into the schema context. At least one of them is not fully valid with respect to a schema corresponding to the Schema for Schemas.
ACTIONCheck the errors reported when schema documents were loaded, mapped, or validated. Correct errors found in the identified schema documents and reload them into a new schema context. Then provide the new schema context to the processor.