Pro boosters all at 10% of router speed

[Toweliechaos]

So, in the kitchen this morning and thought I'd do a speed test as the Internet radio wasn't giving all the information I would expect. It came back at 3mb with a router link speed of 50. I went to the router to check there and sure enough got 40+.

Rebooted the booster, no difference. Checked another booster elsewhere in the house and the same crap speed. 

The boosters are all backhauled via powerline adapters and report "excellent" connection. 

Before I have to spend hours of my life waiting to talk to 'experts' who will probably factory reset my router without asking (again), does any sane person have a suggestion of what to do or try? 

[CrimsonLiar]

So, how many boosters do you have?  Generally the fewer you can use to get the coverage you need the better!

Have you tried without the powerline backhaul, and have you actually tested the powerline devices directly, and tried a different cable between the powerline device and the booster?

Is it possible the internet radio is not connecting to the booster but to the main router, due to channel 12, 13 problems (are your boosters on the same channel as the router?).

[Toweliechaos]

I have three due to size and type of house. However, further testing has revealed that both of the upstairs boosters are transmitting decent speeds and it is just the one booster that is delivering <10%.

I assume a factory reset of said booster would be the first option?