HG633 Slow WiFi speeds.

I'm experiencing very slow speeds on my WiFi connection, less than half the speed of wired. It's been like this since I signed up with Talktalk.  I have tried different wireless channels and freqencies 5ghz and 2.4ghz with the same results, its the same speed with all devices, laptops phones etc...sometimes dropping right down to under 1mbps! And the error count in the router statistics doesn't look good either. This seems to be a common problem with these routers possibly a bad batch. A replacement router would be greatly appreciated.

I've added screenshots of speeds and error counts.

Wireless ERRORSWIRED SPEED TEST

WIRELESS SPEED TEST

Thanks.