Hello.  I just got a set of 3 eero Pro 6.  I have gigabit ethernet with my ISP.  After a couple of days I noticed that my internet speed through my ethernet devices dropped from ~950 Mbps up/down to about 700 Mbps.  I restarted my ISP modem and that didn't fix anything so I connected my laptop directly to the ISP modem and I got my regular speeds again (~950 Mbps up/down), but when I connected the laptop to the other ethernet port on the eero gateway; the port that is not connected to the ISP modem, then it went back to  700Mbps so it looked like there was an issue with the eero gateway. 

I swapped the eero gateway with another eero Pro 6 router; the speeds went back to normal ~950 Mbps up/down but after a couple of days the speed went back down again to about 700 Mbps.

The other 2 eeros are connected to the eero gateway via ethernet.  On the eero gateway one port goes to the ISP router and the other port goes to a switch.  The other 2 eeros are connected to that switch via ethernet and then the other port of the eeros goes to a switch in the room where the eeros are located.  (See image)

To test if the issue was with the switches and/or the ethernet cabling, I connected my ISP modem directly on to the switch where all the eeros are connected.  Each port on that switch goes to the other 2 eeros and the to a switch for each eero.  I disconnected the eeros from their switch and moved the eero ethernet cable directly to the switch.  When the ethernet devices are connected directly to the switch and then to the ISP router, the speed was always ~950 Mbps up/down ruling out that there was an issue with the switches and/or the ethernet cable and/or the ISP modem.

Has anybody had this issue?  I contacted eero support but it takes them a couple of days to reply and the suggestion that they make is the typical: "restart your router".

Sorry for the repetitive description of my network but I wanted to be as clear as possible.  

Thanks.