sHello,

Did you let the WTFast system run for any length of time? It may be the WTFast client was updating or getting config/system refreshed. My guess is that the client on the router, is not a multithreaded client, and therefore it could only utilize 1 CPU to do it's work, and that eventually it should settle down.
Another thought is this could be exactly what needs to happen to make the WTFast system work. Dedicate a single CPU to Gaming and QoS traffic. Thus taking advantage of the gaming hardware, rising above the opponent to crush their dreams of victory. Ha Ha Ha..

I did notice that WTFast did put a load on the device, but I did not check CPU/RAM usage. I expected something to change when activating that option. I don't see the need for WTFast on my network, and don't want the extra cost to use it. So I turned it off. When we're all gaming on the network (4/5 devices) I will switch on the Gaming QoS functions, when I hear a complaint. Honestly, rarely get a complaint about the network speed. The network mostly gets used for Media so by default I run with Media as the QoS option and I have prioritized network usage for each device. IoT gets the lowest, and it goes up from there, depending on the Parent/Child/Spouse hierarchy. And of course, the Queen of the house, my wife, is first in line. As they say, Happy Wife, Happy Life.. 🙂

Be @ Peace
Trav..