RT-AC68U crashes and necessitates re-Powering the router

I purchased an an RT-AC68U to replace an RT-N-66U 2 weeks ago and have been having problems with it ever since.

I am running 4 computers, 2 via WiFi & 2 via direct Ethernet connection. In addition, I have a Roku, 2 WD Live Streaming Media Players, a Chromecast, several phones & tablets, and 2 thermostats that are clients of AC-68U. I'm using Merlin's latest build 378.56-2.

I've had numerous problems with the router. 3 times a week, it crashes for no reason. I lose Internet and Intranet....

RT-AC68U crashes and necessitates re-Powering the router