I have roku ultra on a vizio red 4k hdtv. When attempting to stream live tv channels on Sling, the roku crashes. It does the same thing on some other apps, but not all. Also, I wonder if there is an incompatability problem with vizio as I have 2 vizio tv's. on the 4k red smart tv, now the tv's native "SmartCast" doesn't work. I put the roku on my old 1080p "dumb" tv and get the exact same results. It appears that on demand is fine, and live streaming still works on other apps like Pluto and CBSNews.