What's your wifi client?
You're testing with wifi client side by side the router?
How congested is your wifi environment?

Sound like congestion to me. Likely your surrounding wifi environment is busy with many APs. If you use inSSIDer, how many wifi APs do you see?

Also your wifi client? Is it N-150 or N-300?

Interesting... must be some non-wifi interference. I can get about 40Mbps over wifi (transfer from my NAS on wired to my PC on Wi-Fi over 10m in between a wall). So your homeplug has wifi as well? If yes, what's the speed you're getting from it?

by the way, you still haven't say what wi-fi client you're using...

Maybe a better router can be a solution if you're ok to fork out the cash. the good ones in WiFi are the Asus ones, you should look into dual band solution (N56U, N66U, AC56U, AC66U)

Donate the "homeplug" to me ok ?

Use the homeplug to get coverage.

I also use 3 routers. One is the lousy thompson to provide internet (with wifi off), then LAN out to another 3x3 router for first floor WIFI and then LAN out to homeplug to connect to the third router for ground floor WIFI.

Use 5GHz also good, prevent interference from neighbours' router which are usually stock router which runs on 2.4GHz.

Replacing one crap with another crap? Why not get Asus RT-N16 based on Broadcom chipset? Seem to get a lot of rave reviews worldwide.

Only if you don't want to use the phone...

Then you can do it the easy way, i.e. route the Thomson/Technicolor (wifi disabled) as WAN into your own wifi router. Or you can setup your own router to replace the Maxis stuff (the harder way).

Share your findings when you have it all setup...

Is it good?

Im eyeing AC68. Wonder if thats really necessary.

Actually I already got two pretty good router. DIR655 and Apple Time Capsule which I bought during SiS warehouse sale few years back.

Im planning to cover the whole house with just a single router but if I did that, those two, plus the homeplug will be useless. Sigh...

You mean your maxis fibre??????

I don't think it is a sabotage, they don't get anything by sabotaging Unifi customer. I had problem before when migrating from Unifi to Maxis, I had it to parallel run it for couple of months before decided that I should terminate the Unifi. Since Unifi and Maxis has different setup, they also changed the fibre modem password on their side but without updating it on my modem. This I blame it on the uncompetent Maxis installer. He should've follow the procedures and not by checking that everything was working okay and that should be it. No auth/link can be caused by physical disconnection too. So, nothing much you could do other than calling Maxis and have an appointment with both Unifi and Maxis technicians again.