miconda left a comment (kamailio/kamailio#4102)
I have most of deployments with an edge proxy/load balancer that sends out SUBSCRIBE requests to the main registrar/presence server, not facing such issue. Above are couple of backtraces pointing to different places in the code, so they do not identify the issue, probably they are a side effect of an early fault operation (e.g., buffer overflow).
Is this stock Kamailio? You don't have custom modules or patches, right?
Also, do you send out a SIP request to more than 12 destinations?