When endpoints register through a proxy in front of Asterisk running PJSIP, the edge proxy adds a PATH header so that Asterisk knows how to route out-of-dialog requests back to the proxy.
When calling that endpoint, it appears though that INVITEs are sent to the Contact URI directly instead of being sent to the proxy with a preset Route header. Strangely, this happens only to INVITEs. Other requests such as the OPTIONS qualify initiated by Asterisk are sent correctly to the proxy with the proper Route header.
When using chan_sip this problem does not occur.
PJ_VERSION : 2.7.2
AOR/support_path : true
Endpoint/rewrite_contact : false
Endpoint/force_rport : false