Sky Q box randomly powers off

[Ray+French]

My SkyQ box randomly powers off and message says no signal, it must be unplugged and rebooted which works immediately. Recordings randomly fail due to power cut when there has been none. After switching to standby overnight using remote it will usually not restart in the morning. All setting have been checked with sky advisors. The SkyQ box has been replaced three times now by Engineer and still the problem persists. There are no ventilation issues.