Still no improvement after the channel change from Quick Fix 5? Give this a try...
Could you go wired?
Wired connections are more reliable than a wireless connection, this is because a wireless connection can encounter interference from things in your property.
Have a move around!
Routers work using high-frequency radio signals. Like all radio signals, it's possible for them to pick up interference. This can be caused by all manner of electrical appliances, including; microwave ovens, security cameras, Bluetooth devices, cordless phones and baby monitors.*
*Top tip: Make sure you move your router away from any of these devices.