I don't think it is a bug. There is misunderstanding... http://forum.tp-link.com/showthread.php?80417-Address-Reservation&p=158683&viewfull=1#post158683

There is a next button according to the emulator. You cannot see it? How many enties you add in total? Can you provide the screenshot as well?

When WA901ND works in repeater mode, the SSID will be the same as main router's SSID and it cannot be changed. WA850RE can meet your requirement because it allows us to customize the extender's SSID.

What's the operating system of your PC? All other options displayed on utility are grey out except the one you mentioned, right? Take Windows 7 as an example and try to enable WLAN Autoconfig....

TL-MR3420(Four-Address Format WDS) cannot WDS C9(Three-Address Format WDS) successfully.

You'd better try different web browers to login the web interface. Ensure the connection between WPA4220 and PC is stable enough.