TP-Link disables WiFi and restarting

I have two issues with my TP-Link TD-W8960N router (Firmware Version: 1.1.1 Build 131129 Rel.49672, Hardware Version: TD-W8960N V5 0x00000001):

1. From time to time (not regularly, once per week, random time) WiFi is set to disabled (Menu Wireless > Basic > Enable Wireless is unchecked). When I turn it on, all the settings are remembered and WiFi starts to work again. Interestingly, it won't happen if I hard reset my PC.

2. When I shut down my PC (not laptop, Mac or whatever), the router always restarts its PPPoA connection. In the logs there is a lot of entries similar to:

   kernel: Intrusion -> IN=pppoa0 OUT= MAC= SRC=216.243.31.2 DST=[my IP] LEN=40 TOS=0x00 PREC=0x00 TTL=240 ID=54321 PROTO=TCP SPT=49658 DPT=443 WINDOW=65535 RES=0x00 SYN URGP=0 MARK=0x8000000
   

These logs say (if I'm correct) that the router is doing its job - but what about restarts?

I have no idea what is going on. I'm running Windows 10, virus protection is enabled with Avira, and I've completed a full virus/spyware scan. I've also changed the password and SSID a few times but nothing has changed. How can I fix this?