I have exactly the same issue. Samsung 4kTV, X1 box. Several visits, box change and nothing corrects the issue for more than 24 hours. I use the "My Account" app to send a restart signal to the box, wait the 5 minutes for everything to reload and then it works fine until the next day. Turning off power savings, changing resolution, using different HDMI cables (and ports on the TV) and a new surge protector (all suggested by various Comcast technical support folks) had no effect on the problem. It is very frustrating to have to do this every time we watch Xfinity. Roku, Applet TV and Samsung DVD player all work as designed with any of the HDMI cable or ports on the Samsung set.
... View more