From support case https://support.atlassian.com/browse/IDESP-137. Customer of OnDemand tries to connect to their JIRA using IntelliJ Connector. On testing the connection (which amounts to a SOAP-based login), they get the response code like the one in summary. This seems to be the same response as ones in JRA-25048 and JRA-26770. However, these issues seem to happen when JIRA is being restarted. I am not sure if this is also the case here - maybe it is, maybe it is not. Anyway - the error code originates from somewhere inside JIRA and bubbles to the SOAP response and back to the remote client