Sounds like DLNA compatibility issue. As I know, TD-W9980 doesn't use standard DLNA module, which may cause the problem like yours.

As I read the user guide, there is URL filter but it seems that it cannot block a specific PC. http://www.tp-link.com/resources/document/TD-W8151N_V3_User_Guide_191001.pdf

Any problem with your internet connection? If no problem at all, just ignore the message in the log.

BT infinity fiber or Standard BT? In UK, most ISPs use PPPOA as the connection type. In this case, we need to configure it on modem router because the router doesn't support PPPOA. Thus, if you...

If you have selected Time Zone and configured NTP server correctly, after press Get GMT, correct time will be obtained. It won't lost even you reboot the router. It may takes a few minutes to obtain...

They are compatible with each other. No worries. You can pair them or rename them. http://www.tp-link.com/en/faq-258.html