Probably the field `dst->send_sock` is no longer valid, it can confirmed by getting:
``` frame 0 p *dst->send_sock ```
If the address is invalid, can be the case that the SIP transaction is destroyed at same time due to a race.
I see you use dialog mode tracing - `d` mode:
``` # Only start sip_trace on initial INVITE sip_trace("HEP_URL","$ci-MY_IP","d"); ```
Which was not in 5.2.x, so it might be a bug of that feature. I haven't implemented it, so I do not have proper insights at this moment, it will take me some time to get into it. Meanwhile, if you still face crashes, maybe you can switch to tracing using:
``` modparam("siptrace", "trace_mode", 1) ```
and:
``` event_route[siptrace:msg] { if(!is_method("INVITE|ACK|BYE|CANCEL|PRACK|UPDATE")) { drop(); } } ```
as I understood that you want to do sip trace for traffic related to calls.