Hello, Apparently, this is the way the code works: t_reply.c: if (relayed_code==503 && tm_remap_503_500){ /* replace a final 503 with a 500: * generate a "FAKE" reply and a new to_tag (for easier * debugging)*/ Lets see if maybe others can comment as well. Otherwise you could just open an issue on our tracker, it is probably not that hard to change this. Cheers, Henning -- Henning Westerholt – https://skalatan.de/blog/ Kamailio services – https://gilawa.com *From:* sr-users &lt;sr-users-bounces(a)lists.kamailio.org&gt; *On Behalf Of *Gerry | Rigatta *Sent:* Wednesday, July 22, 2020 8:58 PM *To:* Kamailio (SER) - Users Mailing List &lt;sr-users(a)lists.kamailio.org&gt; *Subject:* [SR-Users] bug ? remap_503_500 breaks dialogs Hi, I am using Kamailio 5.2. Apparently the remapping of 503 to 500 codes in the tm module does also change the to-tag. This behaviour breaks dialogs with yate and therefore calls hang and the 503 remains unacknowledged. After disabling the 503 to 500 remapping with modparam("tm", "remap_503_500", 0) all works fine again. Changing the to-tag in a dialog seems to contradict RFC3261, or do I see this wrongly? 12 <https://tools.ietf.org/html/rfc3261#section-12> Dialogs A dialog is identified at each UA with a dialog ID, which consists of a Call-ID value, a local tag and a remote tag…" Thanks for looking into this. Gerry _______________________________________________ Kamailio (SER) - Users Mailing List sr-users(a)lists.kamailio.org https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users