Hi David, This error is created from the dialog state machine, as you already guessed. In the worst case the dialog will be expired then after the expiration timeout. So if you do not getting tons of this errors, it should be not critical for kamailio internal operation. Regarding the SIP race condition, you can lookup the particular RFC (e.g. 5407) and then address it in the UA, if appropriate. Cheers, Henning From: sr-users &lt;sr-users-bounces(a)lists.kamailio.org&gt; On Behalf Of David Escartín Sent: Wednesday, May 12, 2021 8:03 AM To: Kamailio (SER) - Users Mailing List &lt;sr-users(a)lists.kamailio.org&gt; Subject: [SR-Users] bogus event with terminated dialogs with late 200ok responses Hello all using kamailio version 5.4.4, we are seeing some errors like CRITICAL: dialog [dlg_hash.c:1205]: next_state_dlg(): bogus event 3 in state 5 (with BYE) for dlg 0x7f6ca2304b48 [15135:39671] with clid '00463385_20210512_002_HPRA_1.1.4.40.sp3_7532_0_54533900281' and tags 'Out-55089-0000000CB27947F9' '170cB11c48vmj' which seem to be generated when we receive a BYE from the remote UA but we were expecting an ACK also, For example INVITE ----------> <---------------183 <---------------200 BYE -------------> (no ACK) <--------------200 <--------------200 .... so the b2bua (freeswitch) keeps retransmitting the 200ok, and on each 200ok retransmission we are getting this type of message. These seem to be like race conditions since 200/BYE flow almost at the same time, and as I understand, the UA should send the ACK. But my doubt is if these errors can be harmful for the kamailio or they can be ignored and address the issue to the remote UA on each case thanks a lot and regards david -- [https://www.sonoc.io/wp-content/uploads/2020/07/Logo_SONOC_emails.png]<h… David Escartín NOC engineer www.sonoc.io<http://www.sonoc.io/> [LinkedIn]<https://www.linkedin.com/company/sonoc> [Twitter]<https://twitter.com/sonoc_> [Facebook]<https://www.facebook.com/SONOCio/> This e-mail is for the exclusive use of its recipients and may contain business secrets or other confidential or privileged information. Any unauthorised use, copying, publication or distribution of this e-mail is strictly prohibited. If you are not the intended recipient, please inform us immediately by replying to this e-mail and delete it, including any attachments or copies on your system. In accordance with the GDPR (EU) 2016/679 and the LOPDGDD 3/2018, we inform you that this e-mail address and/or any other personal data you have provided us with will be treated by SONOC with absolute confidentiality and with the only purpose of providing you with the requested services, due to your condition as a client, supplier or because you have requested information from us at any time. These data will only be kept for as long as required to comply with legal obligations. You can exercise your rights at any time by sending an e-mail to: dataprotection@sonoc.io<mailto:dataprotection@sonoc.io>.<mailto:dataprotection@sonoc.io>