RB4011iGS WLAN connectivity issues

Good evening

I’ve just installed this WLAN router at an exhibition where we get connectivity supplied from a telco via a Fritzbox CPE.
The setup was done with the initial settings and just changing the SSID…eth1 as WAN port, and others as client ports.

Suddenly the WLAN connectivity went down, though signal strength was perfect as well as bitrate (108mbps), though I couldn’t even connect to the router admin interface…
also oddly the LAN side ethernet ports suddenly got IP addresses from the CPE hooked up to the WAN port…

Had to reset the routers config and hooked up LAN clients to eth6 - eth10 as I think all ethernet ports including WAN ports are bridged together.
At least in the evening the WLAN and LAN connectivity seems to be resolved…

Is this really the case with the initial configuration that eth1 is bridged with the other ports?
Or did I miss some other settings I should have done?

I will see tomorrow morning if the connectivity is still okay or I have to reset again.

Do you mean to say you didnt even change the user name from admin and invoke password protections???