It might be BT kicking you off, I assume you're using FTTP with an ONT on the wall? if so the installs sometimes don't play nice with 3rd party equipment, I'd ask BT to do a line check first so see...

Looks a lot like Go*g*e DNS, use a dns checker and it'll tell you whose handling your dns i.e if you've changed to settings in the router or PC settings your dns will be avoiding your isp servers....

@Wienen Another consideration if it happens again is you can't login to the router from 2 different devices at the same time, if you try to it will attempt to stop the other session, also when this...

@Rubensds68 This may sound silly but without knowing the environment the router is in it could just be getting too hot. If you can try to remember what the room temp is when you have issues vs a...

@Lemur21 I think iirc if the main router is on say 192.168.1.1 the router tagged to it will have to be on 192.168.1.2 or above but not encroaching the DHCP pool number which normally start at...

@Golding It's a good tip, the older TP units used to be ok to do this anyway but the newer gen ones don't seem to accept it done normally & spit the dummy.