Many of the searchParameters involving extensions are incorrectly coded.
All of them should be checked and tested using FHIRPath.

For example: http://build.fhir.org/ig/HL7/VhDir/SearchParameter-endpoint-usecase-standard.json.html

The expression included is:

"expression" : "Endpoint.extension('http://hl7.org/fhir/uv/vhdir/StructureDefinition/endpoint-usecase').extension('standard')",

It should be:

"expression" : "Endpoint.extension.where(url='http://hl7.org/fhir/uv/vhdir/StructureDefinition/endpoint-usecase').extension.where(url='standard')",