I've found that my WIFI extender tends to lose connection with my router. I eventually took it offline. Some devices are super sensitive to fluctuations in network speed. Even a brief slowdown can kill the connection. So your complex WiFi routing may just be too inconsistent with speed or connectivity. Can you connect directly with your router to test?
Also having the multiple EXT addresses may be an issue if it expects to see the router and device on the same network.
Just some thoughts to consider.