3524061 - Error during access to the ref node 'XXXXXXXX'. The ref node is not defined or does not have the necessary type

OData call with $expand and $format=json fails:

500 - Internal Server Error;  In the context of Data Services an unknown internal server error occurred

In /IWFND/ERROR_LOG:
.ERROR_CONTEXT    
..ERROR_INFO    Error during access to the ref node 'XXXXXXXX'. The ref node is not defined or does not have the necessary type
..ERROR_RESOLUTION    
...SAP_NOTE    See SAP Note 1797736 for error analysis
...LINK_TO_SAP_NOTE    https://service.sap.com/sap/support/notes/1797736
..Exceptions    
.../IWCOR/CX_DS_INTERNAL_ERROR    
....Text    In the context of Data Services an unknown internal server error occurred
....Source    
.....Program    SAPMHTTP
...CX_SY_NO_HANDLER    
....Text    An exception with the type CX_ST_REF_ACCESS was raised, but was not handled locally or declared in a RAISING clause.
....Attributes    
.....CLASSNAME    CX_ST_REF_ACCESS
....Source    
.....Program    /IWBEP/CL_MGW_ST_CALLBACK=====CP
.....Include    /IWBEP/CL_MGW_ST_CALLBACK=====CCIMP
.....Line    425
...CX_ST_REF_ACCESS    
....Text    Error during access to the ref node 'XXXXXXXX'. The ref node is not defined or does not have the necessary type

SAP Gateway (OData)

SAP NetWeaver

Unknown, Internal Server Error, ref node, OData, multi-level expand, $select, $format=json, ST Active, SAP Note 3523663, Error during access to the ref node, CX_ST_REF_ACCESS, /IWFND/ERROR_LOG, Gateway , KBA , OPU-GW-COR , Framework , Problem