Most likely it’s the Auto Connect that’s causing the trouble. It basically tries to ping the router and see if it’s still connected. This feature is implemented in the first place because in case there is a power break, and the controller is powered on before the router is, it should be able to re-establish IP from the router.
A quick work-around is to set a static ip on the controller (note, this only works if you set a static ip on the controller, not by using IP reservation on the router), you can turn off auto-connect, and since the ip is fixed, it doesn’t need to be re-established. This is probably the best option if you are still seeing freezing problem.