Why Chromecast does not work properly?
Every movie/tvshow has its own video codec and list of audio codecs.
Chromecast can support only special amount of them, while some of the content Chromecast support, some of it, it doesn't.
Generally our tvshows are MKV which should support via Chromecast, while the movies are MP4.
We suggest you to use different type of solution, like getting a proper android device and use it on the television you'd like to watch on.