I have an issue with attended transfer, sometimes it fails, when comparing the wireshark traces for working and non-working cases I found this Error message “500 Overlapping transaction not allowed”.
Could you please advise what can be the cause of this ?
What version of Asterisk? What channel driver are you using (if 13)? What is the SIP trace (sip set debug on, or pjsip set logger on - depending on channel driver).