FS-3664 found the place I was talking about in sofia_glue.c, update to latest…

FS-3664 found the place I was talking about in sofia_glue.c, update to latest and try setting t38_passthru=once

src/mod/endpoints/mod_sofia/sofia_glue.c

@@ -4432,14 +4432,18 @@ uint8_t sofia_glue_negotiate_sdp(switch_core_session_t *session, const char *r_s
 				int pass = sofia_test_pflag(tech_pvt->profile, PFLAG_T38_PASSTHRU);
 
 				if (var) {
-					pass = switch_true(var);
+					if (!(pass = switch_true(var))) {
+						if (!strcasecmp(var, "once")) {
+							pass = 2;
 						}
+					}
+				}
+
 
-				/* can't remember if this is necessary but its causing a bug so i'll leave this comment here to remind me
-				if (sofia_test_flag(tech_pvt, TFLAG_T38_PASSTHRU)) {
+				if (pass == 2 && sofia_test_flag(tech_pvt, TFLAG_T38_PASSTHRU)) {
 					pass = 0;
 				}
-				*/
+
 
 				if (switch_channel_test_flag(tech_pvt->channel, CF_PROXY_MODE) || 
 					switch_channel_test_flag(tech_pvt->channel, CF_PROXY_MEDIA) || !switch_rtp_ready(tech_pvt->rtp_session)) {