1) My old Netgear Router had verbose DHCP details in its Router System Log, which helped when diagnosing (for example) 2 devices trying to use the same IP address. 2) My Sonos Beam wireless WIFI...

@Riley_S Thanks for your standard debugging suggestions. I had hoped that my answer did more than hint at the debugging which I had previously attempted. You did not mention swapping the two...

I have 2 x TP-Link AV2000 V4.8 2-port Gigabit Passthrough Powerline Adapters. ALl of the time my throughput between all Adapters is yellow (>50 Mbps), except FROM the Fam_Room to the Kitchen (<50...