@Alexandre. Thank you - I tried it with an older 2.4 Ghz router as you suggested and it worked, however it was about 10x slower than when the device connects to the furthermost Deco upstairs so it...

Would it be possible to remove one of nodes and add it back in as a new network in access point mode, and then have the device connect to that node only? (obviously losing the roaming but that...

The product page says "Devices automatically switch between Decos as you move through your home for the fastest possible speeds." This is the reason I purchased a 3-pack of the M5 Deco, and at least...