I'm on Chorus fibre via an HG659 modem. It works well on most of my devices, including an older PC.
On a new Win10 PC, though, I've been plagued by slow connections and entire sites not loading at all, while most other sites work perfectly fine. One of the common threads was almost anything Google-related (including CDN host servers for CSS fonts, which was why it was affecting several other sites). Another symptom was that the Chrome Web Store wouldn't load thumbnails for any extensions, and would also fail to install any extensions.
Looking at the network traces, sometimes a connection went through ok, sometimes it took 30-40 seconds to get a response, sometimes it timed out after about that long, and sometimes it just dropped the connection within seconds.
The common thread seemed to be IPv6. All the bad connections were using IPv6 destination addresses.
I'm reasonably sure I had IPv6 disabled on my previous PC. I tried disabling it on my new PC (just by unticking it in the network adapter), and lo and behold all of the problems vanished.
Does this issue sound familiar to anyone? Any ideas of other methods to resolve it?