Grandstream GXP2130 not dialing out via IPSEC VPN

Good afternoon…

I have the following scenario that seems to be troubling me quite alot.

I have a working IPSEC VPN connection through a CCR1009 and RB4011 two remote sites.

Lets name the sites

CCR1009 SITE A with IP 172.21.1.1 172.21.0.0/16
RB4011 SITE B with IP 172.11.1.1 172.11.0.0/16

SITE B has a VoIP PABX Yeastar S412 with an IP of 172.11.10.99
I have two SIP extentions created on the PABX network.
Extention 9
Extention 10

I am registering these extentions with SIP port 6060 instead of 5060 i.e Ext 9 uses SIP Server 172.11.10.99:6060

The soul purpose is to take a GXP2130 Grandstream device and Register ir remotely on SITE A with extention 9 and a Zoiper Account on SITE A with extention 10.

My problem is as follows

The GXP2130 registers through the IPSEC tunnel but fails to Dial Out.
It receives incoming calls from extentions from site B though without any problem and voice passes through just fine.

The Zoiper extention on the other hand (extention10) has no such issues. It can dial out from SITE A and receive calls from SITE B so it can’t be a port problem.

Bot sites ping each other and its devices just fine.

i.e 172.21.1.1 pings 172.11.1.1 and vice versa
172.21.1.1 pings 172.11.10.99

I failed to mention that the GXP2130 has a static IP of 172.21.10.100 on SITE A which is pingable also from SITE B (172.11.1.1 pings 172.21.10.100)

Any ideas as to what is causing the GXP2130 not being able to dial out?

Thanks in advance.

Any ideas?

To anyone interested or having the same problem disable all your Custom Sip Headers on the device and it will work.