We upgraded everything freePBX (freePBX and Zulu Server v18.104.22.168, Zulu Client v3.5.0+206). All call merge patterns now work, except one.
Insider-B calls Insider-A, then Outsider calls A. A tries to merge calls and it fails. Outsider hears "Access Denied (?).
I have the logs from Zulu and PBX available if anyone is interested.