Q Box disconnecting from WiFi at same time each night

[Coislana]

Our Sky Q keeps disconnecting from the WiFi each night, always around the same time, somewhere between 9 and 9.30 pm. 
It's really annoying!

It's not the WiFi, all over services work and we have done a speed test at the exact time it disconnects and the WiFi is perfect.

Does anyone know what causes it and how to fix it? 

[Chodley]

"All other" I assume you mean?

Wonder if there is some electrical interference. Do you have a timed water heater or anything coming on at that time or an automated light or some other device?