Hi all
I’ve been wanting to try FreePBX for a while, so finally set it up.
I’m using a semi-custom install - with Debian Jessie (Debian 8.9), and Asterisk 15 (GIT-15-caad08d) - built off the instructions here 
Barring having to force the following in modules.conf,
preload = chan_sip.so
preload = res_rtp_multicast.so
preload = chan_rtp.so
…my PBX is up, with two local extensions (1 x SPA502G and 1 x SPA232D with 3 DECT handsets).
I have a PSTN on the FXO of the SPA232D, and incoming/outgoing calls are working, with CLID (which was a swine to get running). I also have two SIP trunks, both of which are routing incoming/outgoing calls fine.
My problem is blind transfers (via ##)
If I have a call (external or internal) - and do an attended transfer (*2) - it works - I hear the target destination, I hang up and the calling party gets the transferred call.
If I do a blind transfer (##), I get the prompt, then the dialtone. The other party is put on hold (with MOH) whilst I dial the target transfer - but the minute it completes, my call terminates and the caller gets congestion and is dropped.
I’d like to post my log but I can’t post links (new user!), and the log is “too big” - so not quite sure how to post the diags? I’ve logged everything from the point of dialling (from ext 6001, to ext 6000) and the drop. I’m trying to transfer to a custom destination, 667 (six six seven)
Log line 526 has the ## detection.
Log line 625 has “667” detected
Log line 866 shows Congestion playing to 6001, with soft hangup.
All help appreciated! (especially with how to get the diags viewable!)