What would make the wifi perform slower on the satellite deco units compared to the main one? These things are using powerline backhaul so it should negate the problems faced by other two band mesh networks. By slower I mean on devices connected via wireless to the satellite deco doing a lan speed test to rule out internet speed fluctuations.

Interestingly if I connect a laptop via ethernet cable to the satellite then the speeds are much faster, it's just the wireless clients having problems or facing limitations of the deco system. If I connect these same clients to the main deco using the connection preferences in the app then they have much faster wireless speeds, I conducted these tests right next to the deco units to make it fair and have tried both 2.4ghz and 5ghz bands but the results are the same.

Topology, they are connected via PLC and wifi.

tl;dr: Satellite decos have much slower than expected wifi throughput compared to the main deco.