We found incorrect STUN behavior of the WebRTC phone.js functionality regarding send-receive dialog with an STUN servers.
No any STUN respond. Probably syntax mistake? Was tested WebRTC phone.js (FOP2, incorrect behavior), and SIPML5 phone (Dubango. correct behavior) with stun.l.google.com:19302 and stun.sipgate.net
Besides, for WebRTC FOP2 local ringtone need to change:
variable e.reason_phrase should be change to e.reasonPhrase (line 26 in /var/www/html/fop2/admin/plugins/phone/webrtcphone/js/phone.js )
**< if (e.reason_phrase === 'Trying') {console.log("----->Trying");
if (e.reasonPhrase === 'Trying') {console.log("----->Trying");**