ADSL light is not on when connection drops, right? Did you try to change DSL mode to ADSL2 or G.DMT? If it won't work, maybe it is faulty. Go back to your vendor and confirm if it is still under...

Martin, do you know your printer is not in compatibility list? http://www.tp-link.com/common/compatible/print-server/

V4 can ONLY upgrade firmwares for V4 and it CANNOT upgrade firmwares for V5.

How did you test remotely to access management page? http://www.tp-link.com/en/article/?faqid=308

Your understanding is right. W8961NB cannot be a VPN client or server.

Unfortunately, I don't think so...Buy a new one then...