Seems to be Ethernet related. I can use WiFi as much as I want, can transfer files to Google Drive etc but if I go to some sites such as Facebook on my PC which is wired (Giga-Ethernet) then the link drops.
Already using high quality Cat 6 cables. Cables are nothing to do with it, they've been fine until the Firmware upgrade, as you can see, going to certain sites is the cause. Cables absolutely not a part of this!