There is currently a workaround in place for
IDB-731 due to the expression visitor handling when GetMultiKeyValue is called on fields that are not populated. This needs to be eventually updated so that it doesn't throw a null reference exception in this case.
A null reference exception can also be produced by calling doing an "entity.GetMultiKeyValue(key) != null" check. This can be reproduced by readding this check to EntityCompositeKeyDistinguishedNameStaticRelationValueAdapterBase.Transform and reattempting the scenario described in
Customer support service by UserEcho