Once we got console access we found that the eth0 could no longer ping the local lan and the mirroring traffic on eth1 was no linger containing SIP data.
We found that the eth1 was showing LAN traffic and a tcpdump of eth0 showed the SIP traffic.
This server has the settings configured to use the ETH names as eth0 and eth1:
GRUB_CMDLINE_LINUX_DEFAULT="net.ifnames=0 biosdevname=0"
We changed the /etc/network/interfaces file and swapped the eth0 for eth1 in this file. This allowed the correct IPs to be available on the LAN and Mirror interfaces.
The Mirror interface is now eth0 and the recording software was updated to start recording interface eth0.
Rebooting the server made it available on the LAN and the recording started working.