FS-4053 try this

src/mod/endpoints/mod_sofia/mod_sofia.c

@@ -495,12 +495,16 @@ switch_status_t sofia_on_hangup(switch_core_session_t *session)
 		val = switch_channel_get_variable(tech_pvt->channel, "disable_q850_reason");
 
 		if (!val || switch_false(val)) {
-			if (switch_channel_test_flag(channel, CF_INTERCEPT) || cause == SWITCH_CAUSE_PICKED_OFF || cause == SWITCH_CAUSE_LOSE_RACE) {
-				switch_snprintf(reason, sizeof(reason), "SIP;cause=200;text=\"Call completed elsewhere\"");
-			} else if (cause > 0 && cause < 128) {
-				switch_snprintf(reason, sizeof(reason), "Q.850;cause=%d;text=\"%s\"", cause, switch_channel_cause2str(cause));
+			if ((val = switch_channel_get_variable(tech_pvt->channel, "sip_reason_str"))) {
+				switch_snprintf(reason, sizeof(reason), "%s", val);
 			} else {
-				switch_snprintf(reason, sizeof(reason), "%s;cause=%d;text=\"%s\"", tech_pvt->profile->username, cause, switch_channel_cause2str(cause));
+				if (switch_channel_test_flag(channel, CF_INTERCEPT) || cause == SWITCH_CAUSE_PICKED_OFF || cause == SWITCH_CAUSE_LOSE_RACE) {
+					switch_snprintf(reason, sizeof(reason), "SIP;cause=200;text=\"Call completed elsewhere\"");
+				} else if (cause > 0 && cause < 128) {
+					switch_snprintf(reason, sizeof(reason), "Q.850;cause=%d;text=\"%s\"", cause, switch_channel_cause2str(cause));
+				} else {
+					switch_snprintf(reason, sizeof(reason), "%s;cause=%d;text=\"%s\"", tech_pvt->profile->username, cause, switch_channel_cause2str(cause));
+				}
 			}
 		}
 

src/mod/endpoints/mod_sofia/sofia.c

@@ -581,6 +581,14 @@ void sofia_handle_sip_i_bye(switch_core_session_t *session, int status,
 	sofia_set_flag_locked(tech_pvt, TFLAG_BYE);
 	call_info = switch_channel_get_variable(channel, "presence_call_info_full");
 
+	if (sip->sip_reason) {
+		char *reason_header = sip_header_as_string(nh->nh_home, (void *) sip->sip_reason);
+
+		if (!zstr(reason_header)) {
+			switch_channel_set_variable_partner(channel, "sip_reason", reason_header);
+		}
+	}
+
 	if (sip->sip_reason && sip->sip_reason->re_protocol && (!strcasecmp(sip->sip_reason->re_protocol, "Q.850")
 															|| !strcasecmp(sip->sip_reason->re_protocol, "FreeSWITCH")
 															|| !strcasecmp(sip->sip_reason->re_protocol, profile->username)) && sip->sip_reason->re_cause) {
@@ -981,7 +989,6 @@ static void our_sofia_event_callback(nua_event_t event,
 	case nua_r_unregister:
 	case nua_r_unsubscribe:
 	case nua_r_publish:
-	case nua_i_cancel:
 	case nua_i_error:
 	case nua_i_active:
 	case nua_i_terminated:
@@ -989,6 +996,19 @@ static void our_sofia_event_callback(nua_event_t event,
 	case nua_i_prack:
 	case nua_r_prack:
 		break;
+
+	case nua_i_cancel:
+
+		if (sip && channel && sip->sip_reason) {
+			char *reason_header = sip_header_as_string(nh->nh_home, (void *) sip->sip_reason);
+			
+			if (!zstr(reason_header)) {
+				switch_channel_set_variable_partner(channel, "sip_reason", reason_header);
+			}
+		}
+
+		break;
+
 	case nua_r_cancel:
 		{
 			if (status > 299 && nh) {