It is a known issue by TP-LINK support team. Your guys can submit a ticket here directly. http://ticket.tp-link.com/index.php?/Tickets/Submit

That's interesting... If there is any update, let me know. Good luck...

D7? You have to configure a static IP for NAS or not? What's the IP address of NAS? After you change the new router, did you change it to be the same subnet as other devices like Windows and Linux...

You enabled WDS bridging on WR841ND? Can you provide a screenshot of Wireless Settings page? WR841ND has no client mode that doesn't broadcast its own Wi-Fi. Can you uncheck Enable SSID Broadcast?

It seems that there is misunderstanding... As I said, if lights are still abnormal after we reset the device to factory defauts settings, it may be defective and we can replace it. In your case,...

Topology is important when we try to figure out the problem with VPN connection... IPsec VPN is configured on W9980 or you just use its VPN passthough feature? W9980 is working as a wireless router...