On my new 55C8, if I use IPV6, it mess up totally the automatic internal network. it's very buggy.
My network is on 196.168.1.xxx and it choose everytime another subnetwork (192.168.0.xxx with the wrong gateway).
If I change it manually , it works, but everytime I turn off/on the tv, it overwrite my manuel settings.
To keep my manual configuration I had to disabled IPV6.