Try to upgrade the latest firmware for WR841N V9. http://www.tp-link.com/en/download/TL-WR841N_V9.html#Firmware

Archer C5 or any other model? V2 is the newer than V1.2 and there are some hardware changes. V2 should work better in Wi-Fi performance.

1. Is the drive compatible with D9? http://www.tp-link.com/en/faq-603.html 2. How to access to the driver? http://www.tp-link.com/en/faq-648.html

Can you describe in details?

After upgrade, reset it to factory defaults and try again. If the problem continues, report it here. http://ticket.tp-link.com/index.php?/Tickets/Submit

As I know, BT Hub 4 is a modem router while MR3220 has no modem function. You should buy products like TD-W***? Your ISP is BT infinity fiber broadband or Standard BT Broadband? If it is BT infinity...