Hi sorry if I'm using poor LAN language.

I find that plugging in a second "router" breaks the internet connection - is that possible or just a coincidence?

UFB -> Asus Modem/Router -> wifi x3 

           Asus Modem/Router -ethernet-> Safesurfer "router" -> wifi x 2

           Asus Modem/Router -ethernet-> Xbox

           Asus Modem/Router -ethernet-> PC

           Asus Modem/Router -ethernet-> TV

The devices that don't get internet are mainly Apple iphones and ipads. The windows PC/Xbox/TV works 100% fine. Windows laptops on wifi are usually ok but sometimes randomly don't get internet.

The solution seems to be unplug the Safesurfer router (keep it unplugged), reboot modem, everything ok. Then after a few weeks i decide to test out the theory, plug in the Safesurfer, and within a couple of weeks the internet breaks. Exclude the safesurfer + reboot -> everything fine. (In the past if i don't exclude the safesurfer rebooting only the Asus fixes Windows wifi but does not fix apple wifi).

Any ideas?😕