I've had Comcast for many years. One of the nice features has been leaving on a favorite news channel when turning off the TV and then when turning the TV back on the next day, having the ability to rewind and go back one hour to see what you may have missed and then catch up. In the last week, we've discovered that when turning off the TV and then turning it back on, the ability to go back and rewind is lost, the Live TV "resets" to when you turn on the TV. You can see where Live TV would have gone back, but it's no longer "blue" and your starting point is now when you turned the TV on. As long as the TV is on, Live TV starts to record and you can go back, but when you turn off the TV it resets again. How can I get back that "Live TV" rewind ability without leaving on the TV?
I would recommend to disable HDMI-CEC feature, which can be found here:
Settings -> Device Settings -> Power Preferences -> HDMI-CEC.
Please, let me know if it didn't help
Another option that you may try is to disable Power Saver (if it's enabled):
Settings -> Device Settings -> Power Preferences -> Power Saver -> Off