BTWholeHome Wifi wired connection drops speed

[ncka]

I have four BT Wholehome wifi discs - three of them are hardwired into LAN ports. The Virgin Hub3 (500 mbps) is connected to a Netgear Managed Switch which in turn feeds to the LAN ports.

I have noticed that the Link speeds for two of the connected devices drops to 10/100 mbps, it fairly random. 

If I unplug the devices from the LAN ports, the speed returns to full speed. However it drops after a few hours. 

It looks like the wired discs are renegotiating the link speed with the switch. Is there a way to turn it off?

[Les-Gibson]

"Can I connect more than one disc to my hub (router) using the Ethernet cables?

If you're using Premium Whole Home Wi-Fi, you can't. Only your first disc can be connected to the hub (router) using an Ethernet cable. If you wish to connect more discs by Ethernet, you'll need to connect them to the Ethernet port on another disc"

Ref: https://www.bt.com/help/user-guides/bt-whole-home-wi-fi-faqs---set-up-and-installation

[ncka]

I'm using the WholeHome wifi, so I assume this doesn't apply to me.