I've seen a statement somewhere that the RF signal used to carry the Ethernet data has to be connected to the neutral wire because it is common to circuits using any of the three phases. So if you can observe a difference in throughput on the same socket-to-socket distance (electrical, of course) depending on whether the sockets are on the same phase or on different ones, it may be worth it to turn the plugs 180 degrees and try again. I don't know your country - in some countries the position of phase and neutral in the socket is standardized and you can insert a plug with protective earth contact to the socket two ways, in others there is only one way to insert the plug and the position of the phase and neutral may be different than the one used in a multi-marked HomePlug product.
Instead of writing novels, post /export hide-sensitive. Use find&replace in your favourite text editor to systematically replace all occurrences of each public IP address potentially identifying you by a distinctive pattern such as my.public.ip.1.