The field '|0' for method '|1' in the view group induced by the SpecificFinder '|2' in the entity '|3' is not representable ...

The field '|0' for method '|1' in the view group induced by the SpecificFinder '|2' in the entity '|3' is not representable as an SPField for an external list, but is a required field. The method is not suitable for create/update in an external list, and will be skipped.