on 03/12/2018, The Natural Philosopher supposed :
crap router software.

try a different router or upgrade its firmware

I use a BT Home Hub 5 Fibre with LEDE OpenWRT installed, as my main
router connected to the line. That has been absolutely stable since my
move to fibre in August. I have though had a constant issue with its
802.11bgn Wifi seeming to disconnect irregularly and almost daily, from
my webcam and needing to be restarted. I just haven't been able to get
to the bottom of this, the 802.11nac port is completely reliable.