Left home for a week, returned to Roku (on a TV not used by anyone else) "blinking" to full black screen every two seconds. TV and HDMI cable are fine. Reset Roku. During Roku start up animation no blinking. Only upon submitting Wi Fi password does blinking begin. Nothing wrong/ changed with Wi Fi as far as I know (and content plays). Pattern changes during video auto detect step (triple blink with longer interval, maybe 2.5 seconds).