Just sent you the pcap and log file.
So here's the fun part:
When I add `log_prefix="{$mt $hdr(CSeq) $ci} "` to the global section, the problem *no longer exists* but when I comment this out, the problem returns.
This seems to be perfectly reliable to fix & break the issue accordingly.
So needless to say the file I sent you does not include the log_prefix, but it does include the other requested changes.