Mine also shut off daily and requires me to unplug power. (Buttons on remote and app on phone cannot make it restart) It happens overnight or middle of the day, while I am watching or when I am not. Mine goes to a black screen on the TV. Today it made a static sound, screen glitched before shutting off. Other times the screen will have horizontal lines before shutting off.
Roku 3900X Express connected to TV via HDMI (cord changed twice already, have a new 3rd one, still)
Software 9.2.0 build 4806-51 update checked today
Power to Roku comes from powerstrip and an original Roku USB/AC plug
Wifi to Netgear C7000v2 AC1900 - signal strength excellent, download speed 27 Mbps
I have both a 2.5 and 5 MHz wifi available in my router, bandwidth saver is off