After years of excellent service from TPLink powerline extenders we bought a M4 triple mesh system as it's a nuisance having to change wifi on Apple devices when moving from room to room. We have Plusnet 80/20 FTTP package with steady 73/22MB from PN's Hub Two router, no downtime or problems in many years. Before installing Deco I put the Hub Two into bridge mode as recommended.

M4 installation went well, delighted with 72MB coverage throughout whole house (three units on one floor). We then had to disconnect the base Deco to rearrange wiring and on restart we found the units had reorganised themselves with base on left, farthest unit in centre, middle unit on right instead of base centre and slave units on each side. Speed on farthest unit was 4MB (yes, four) and on base unit 30MB. Then red light came up so we decided on complete reinstall after switching off ONT, Hub Two and all three Decos overnight. 

Reinstall was a nightmare, red lights kept appearing and we tried swapping the units around and resetting each with reset button etc. After fourth attempt speed from base unit was back to 72MB but farthest unit was only 34MB. I spent easily eight hours' messing about to achieve this as each device (TV, iPads, printer etc) required re-inputting security details after each reinstall. We unplug all electrics when we are away from home, and being in a rural area we have enough power cuts that we have a standby inverter generator. Our old extenders boot up every time, including when I reinstalled them today. The Deco system goes back to the retailer tomorrow as unfit for purpose, very disappointed that TP-Link should put out such a product.