I'm serving from localhost on Chromebook (using browsersync to serve). I get this error in Chrome

Uncaught ReferenceError: cast is not defined
    at CastPlayer.initializeCastPlayer (CastVideos.js:180)
    at window.__onGCastApiAvailable (CastVideos.js:1645)
    at chrome.cast.fa (cast_sender.js:97)

I put a debugger before castPlayer.initializeCastPlayer(); in the handler for __onGCastApiAvailable. This shows that - most of the time - the cast object is not defined even though the callback is called with isAvailable as true. See screenshot - (the watch area shows the undefined cast object). If I refresh repeatedly, cast is occasionally defined.