Pretty much the title. Using the Twitch or YouTube Android TV apps I can enjoy perfectly fine 1080p@60hz without any hiccup. If I cast a video or a stream however using the integrated Chromecast on the Android TV, it's dropping a bunch of frames making it unbearable to watch.
TV updated to latest softwares (both Android and Chromecast) if that matters. Been that way forever, just started recently to look for solutions.
I own 2 Sony TV's. One is the 850D and the other thew 900E. All I can tell you is Sony TV's are not great when it comes to streaming through Chromecast or streaming in generall through the Smart TV. I use Roku and Apple and avoid the whole mess. They are more reliable and do not glitch.
I love the Sony TV picture quality however when it comes to streaming they really suck.
If you can afford it do yourseldf a favor and go buy a Roku player as it is cheaper than AppleTV but works great. Hook it up and you never have to deal with this stuff again.
Good luck with whatever you do. I don't have any solutions other than that one and I have spent lots of time with these TV sets.