We're currently investigating two issues affecting a small number of Gem users.
ISSUE 1: News Network stream constantly freezing up
ISSUE 2: Casting News Network using Google Chromecast stops after several minutes
While we're investigating these issues we'd like to mention that you can alternately stream News Network on web (casting not supported) here. ( https://www.cbc.ca/player/play/939949635618 )
You can also access News Network (casting supported) from the CBC News app for iOS and Android mobile devices.
And please take the time to look through this help article for common Chromecast troubleshooting tips, and this article for general streaming troubleshooting tips on Gem.