Issues with VOIP

[cchamosfakidis]

Hello community,

I am having some issues with the IP phones. The setup is as following:

-PFsense: 2.3.4-RELEASE-p1 (amd64)
-IP Phones in their own vlan
-PBX: Cloud Service

I have created a couple of outbound NAT rules:
Interface Source Source Port Destination Destination Port NAT Address NAT Port Static Port Description Actions
WAN        VOIP            *                    CloudPBX              *                    Wan Address  *              YES
WAN          VOIP            *                    CloudPBX              *                  Wan Address    10k -20k    RND      RTP Ports

The issue is that some of the phones arent able to register at all, or if they are registered, they might loose their registration randomly. Some phones are registered and some phones arent.
I am completely lost and any help would be greatly appreciated.