Do the access points and the main router use the same ssid? You may try them to different ssid to locate whether just one has the issue or all of them have the issue. The channel of the three device...

Like the modem or the PC/phone connected to the router. It is hard to say when there is a compatibility issue. Disconnect all of them then check the situation.

Did you follow the manual to do wifi clone? You may follow the instruction to do the clone, then the tp-link will have the same wifi name as your main router. http://uk.tp-link.com/faq-398.html...

V1 and V1.20 use different hardware. V1 can't use the firmware of V1.20. AV500 and AV600 are theoretical maximum throughput. AV500 should be enough if the bandwidth from internet provider is just...

You can send it back if there is no device connected to the router, but the issue still happen. If the issue won't happen if no device connects to the router, I suppose it is a compatibility issue...

How do you tell the router lost the ISP settings? Check the virgin media hub with your PC when the router lose internet. It the hub is ok, the problem is on the router. You may try to reset the...