Built-in Chromecast doesn't properly play 4k

[rgledhill]

Last night we purchased a 4k film (Peter Rabbit) through Google Play on my phone, then played it through the built-in Chromecast support on the TV.  And guess what?  Just like iPlayer at 60fps (which doesn't work), and YouTube at 60fps (which doesn't work), it also stutters in exactly the same way described on the lengthy YouTube 60fps thread.  So I'm guessing that the in-built software Chromecast is trying to decode 4k at 60fps and fails too.

Is it possible to force the built-in Chromecast to 30fps, does anyone know?

I haven't tried watching it using the built-in Google Play App as for some reason that didn't occur to me last night  and now I've had a refund on it, I obviously can't watch it again.  I'm sure I've watched some 4k films via the built-in app so I guess this is also a word of advice - steer clear of the built-in Chromecast if you can!

[rgledhill]

Yup, found it fine on my PC, but it shows it's not compatible with any of my devices, and it doesn't turn up when browsing the Google Play store directly from my TV either...