This type of thing is annoying. Spotify is rock solid on mine, the only exception being that I sometimes have to restart the app if I have been casting to a single CC Audio and then want to cast to a group or vice versa. Once it has connected, it never drops. I am also using Plex with my iMac as a server and my iPhone/iPad as remotes. This acts strangely as if I try to cast directly from the iMac the CC Audios are often not visible, but when I do so from the mobile devices they always show up, even though this still represents the iMac casting directly to them (I think!) Are you running yours on 2.4 or 5.0ghz wifi?