I switched to a HG659B and Orbi 14 Mesh set up a couple of months ago. It dramatically improved the WiFi performance in my house both in terms of speed and range.  I live 500M from the cabinet in a rural location, but nearer to 1000M in real terms.  Unfortunately, the internet is dropping out at least once a day both via ethernet and WiFi.  Sometimes it clears itself after ten to fifteen minutes, but other times I have to reset the modem.  This did not happen with the HG630B I'd used previously.  There is no pattern to the times this happens.

I've tried the Spark diagnostic test, but that's kind of daft because you can only use it when the internet is working.

I'd like to stop this happening if possible, but I've run out of ideas, and I am not flash with this stuff in the first place.  

The HG659B has ethernet connections to two computers plus a connection to the Orbi 14.  That takes up the available sockets, but there is also the one labelled Fibre which I assume I don't use.

The Orbi 14 has a hub for a cat door connected to one of its ethernet sockets.  I can't think of any other information that might be relevant.

Thanks for any help on this.