Been battling a weird issue at home for a while now and slowly narrowing it down.

Between around 11pm-12am nightly, the wifi drops in the main lounge, but continues in our other lounge no problem (lounges are at each end of the house and have their own APs). We thought it was when I played Xbox around that time (and there are plenty of articles out there about the XBox killing home wifi) but have since ruled that out.

Below is the part of the home network that's relevant.

ONT /// Unifi USG /// Unifi Switch /// Unifi Switch /// TP-Link Powerline Extender /// Other end of TP-Link Powerline Extender in main lounge /// Unifi Access Point /// Wifi devices around Lounge (laptops, phones etc)

When we have the issue I can see the Access Point in the main lounge go offline in the Unifi Controller, I have recently loaded the TP-Link Tplc utility again and see when the AP goes offline, the utility cant see the other end of the extender. 

Appears the issue is either something with the power or the Extender (but I'm likely ruling this out because it runs perfectly through the morning, afternoon and early evening). I also have disabled the Wifi option on the Extender

Why would it happen only around 11-12 at night? If I leave it and do nothing, everything is fine again in the morning, I havent stayed up to see when the Extender and AP come back online but within the Unifi Controller it reports the uptime of the AP to be weeks so its not actually the AP itself going offline.

I contacted the power company to check the plan we're on as I heard stories about controlled power, they said that starts around 8pm at night, so could possibly rule that out.

I am hoping to remove the Powerline Extenders and run cabling some day soon.