I’ve seen the exact same kind of behavior on a rb3011 of ours, all ether ports on the secondary switching chip goes down for 1/2 seconds then comes straight back up - to fast to actually notice any downtime.

Go to ip >> service and check that “www” is not disabled, by default it should be enabled and set to 80.

Then type in the local IP of your hotspot interface or public ip of the router with the www port.

So - http://(public-ip OR local IP):80