We have a YeaStar MyPBX standard edition V4 in our head office. It has LAN IP 192.168.99.99/24 . There are many phones in the HO which are working well. All those phone are in the subnet 192.168.99.0/24
The problem is in a remote extension YeaLink T22 IP Phone, which has IP address 192.168.41.111/24 and connects to the PBX through gateway 192.168.41.1 (DrayTek VPN router)
This remote phone registers well when it boots up. But after a while, it show (Register failed) in it's status web page while still showing as registered in the PBX CLI console.
Another problem is, when I try to call that remote phone from any extension, I get error 486 (Busy Here) which represents call refusing in the phone.
I have double checked codecs order and everything seems to be ok.
Can anybody please advice how to troubleshoot the issue?