tenant with a lot of troubles calling phones

[topogigio]

Hi,
I've a tenant that makes me crazy, I hope that someone has a good idea to help me

I've a FusionPBX with some tenants working on. All are ok, but one has a lot of problems.
This one is a tenant where two separate offices (connected with two separate lines to Internet) with some phones (most of them Grandstream, and two Gigaset DECT). Fusion is remote on a third site. This office come from a FreePBX local server that didnd't create any problem, and was migrated to this Fusion instance.

We have a lot of strange problems:

1. random times internal calls are terminated with called party busy status, but called phone is free
2. sometimes some phone, after a call, remain "as busy" and does not receive any call until a reboot
3. busy status of other extensions do not respect real status
4. ring groups do not call right phones randomly, but ring only one phone of the group

To remove any NAT issues (after a lot of tests to avoid problems in this area), we created a VPN from the office to the Fusion network, and connected phones via internal IPs through the VPN, but this has not solved.

Offices are connected to Internet via Fortigates, where SIP alg was disabled.

We have this problem from many months and we cannot solve, someone can help us?

thanks

 

[bcmike]

Maybe look at this: https://www.pbxforums.com/threads/phone-goes-busy.4930/