RRC Reportable Rest URL not giving consistent response

We are using RRC Rest Service URL as RPE datasource and using "ValidatedBy/alternative" element (datasource/artifact/traceability/links/ValidatedBy) as RQM Test Case datasource. Sometimes without making any changes, neither in RRC artifact nor in RQM test case, we are getting "<data attribute not found>" message. When we check the URL in browser we find the alternative element is missing. And this behavior is not consistent. Sometimes the same URL of the same artifact is having alternate element and sometimes it is missing. Can anybody let me know if we are doing anything wrong or is there any other way to get the datasource of RQM Test Case that is linked with an RRC artifact?