well just having a quick look at mine - I use v14 firmware, I found v15 casued weird snrm and lower sync rates on my eci line
dhcp- disabled
Lan ipv6 disabled
IPv4 Firewall : Enable IPv6 Firewall : Enable
Being on sky - here's my bridge settings attached
Mine was ex kcom, so I manually removed the password,user,http links for the tr-069 etc..
Apart from that I haven't done anything-my pfsense router is connected to port1 and my monitoring setup runs out of port 4.
Have you set up TBB ping monitor or uploading stats? - when I used my ausus as my router pre pfsense days I used to suffer a lot of packet loss. Once I stopped using that and implemented my pfsense box as my router it resolved the packet loss issue for good.
What cab type are you on out of interest. You could see my packet loss on the tbb monitor
Is your router directly connected to the 8324 - I assume it is. - you could get issues with the home plugs...