FS-3487 gonna guess, try this...

src/mod/endpoints/mod_sofia/sofia.c

@@ -952,9 +952,8 @@ static void our_sofia_event_callback(nua_event_t event,
 			}
 		}
 	case nua_r_ack:
-		if (channel) {
+		if (channel)
 			switch_channel_set_flag(channel, CF_MEDIA_ACK);
-		}
 		break;
 	case nua_r_shutdown:
 		if (status >= 200) {
@@ -4969,12 +4968,6 @@ static void sofia_handle_sip_r_invite(switch_core_session_t *session, int status
 			sofia_clear_flag(tech_pvt, TFLAG_RECOVERING);
 		}
 
-		if ((status == 180 || status == 183) && switch_channel_direction(channel) == SWITCH_CALL_DIRECTION_OUTBOUND) {
-			const char *val;
-			if ((val = switch_channel_get_variable(channel, "sip_auto_answer")) && switch_true(val)) {
-				nua_notify(nh, NUTAG_NEWSUB(1), NUTAG_SUBSTATE(nua_substate_active), SIPTAG_EVENT_STR("talk"), TAG_END());
-			}
-		}
 	}
 
   end:
@@ -5165,6 +5158,14 @@ static void sofia_handle_sip_i_state(switch_core_session_t *session, int status,
 		status = 183;
 	}
 
+	if (channel && (status == 180 || status == 183) && switch_channel_direction(channel) == SWITCH_CALL_DIRECTION_OUTBOUND) {
+		const char *val;
+		if ((val = switch_channel_get_variable(channel, "sip_auto_answer")) && switch_true(val)) {
+			nua_notify(nh, NUTAG_NEWSUB(1), NUTAG_SUBSTATE(nua_substate_active), SIPTAG_EVENT_STR("talk"), TAG_END());
+		}
+	}
+
+
 
   state_process: