Resolution bugs

I was thrilled at first but then the TV starting having resolution issues. On start up its 4k then it's 1920X1080. Now it randomly goes to a black screen for a few seconds and back on. Today in 3 hours it has done this at least 20 times. All running on a brand new GTX 960 with the supplied Seiki HDMI cable. I'm sure to return it because of this issue. Second TV in the last two weeks!