@fjzuberi 

Is the C6 disconnected from the host router or does it lose the settings completely? How did you find it out? When configuring the C6 as an extender, you may use a fixed IP address for it, which would be even better if you set it in the IP range of the host. I mean you can set a static IP for it like 192.168.0.2 if the IP of the host is 192.168.0.1. Try logging into the web page next time if it doesn't connect to the host after a power outage, and check if the WDS status still displays RUN.

You'd better fix the wireless channel on the host router to a clear one to avoid interference, which may also cause the extender to lose the connection.