Solved iOS / Android App Attended Transfer to Outside Number not working

[akakern]

Dear all,

since we updated to v16 some strange issues appear on our and customers PBX.

When you try to do an Attended Transfer via the iOS or Android app to an outside mobile number the following issue occurs:
After pressing Attended Transfer you can call the outside number and speak to them. When you press Transfer nothing happens. If you hit the button several times, the call on line 1 ends and nothing happens.

I managed to get a call from PBX with anonymous number but after accepting the call i was unable to hear anything.
The issue is reproduceable on all our PBX with v16 update.

Firewall Test and SIP ALG is okay. We did not have those problems with V15.5

Does anyone know how to fix this issue?
Thanks in advance

 

[akakern]

Unfortunately i can not edit my first post.

I got the same issue with V15.5, and when i do a blind transfer to an outside mobile number i have no audio.

 

[akakern]

After fiddling around with the SIP trunk options i got it working again.

I had to uncheck "Supports Re-Invite" and "Support Replaces" and check "PBX Delivers Audio".
In the extension option i had to enable those 3. Afterwards forwarding (blind and attended) worked again with audio in both directions.