External third party service is occasionally getting
Server returned HTTP response code: 500 when it does a POST to salesforce webservice class, but only occasionally. Most of the times it is working fine.
https://domainurl/services/apexrest/classname . Here,
domainurl is a public site url.Hence, whenever this webservice gets executed, it always gets executed by the same `Guest USER'
How can I debug such error especially when everything works out I am trying to post. AND Is there any way I can make a log in salesforce whenever such error is sent out?