Hi @Danysahne and others i have no doubt!
Solution!!! (FOR MAC and possibly PC)
This may be a bit laborious but works!
This also solves the 'Device Missing; issue with Chromecast
Rollback your Chrome to version 49 or 50.
here is the download site for Mac, Windows and Linux:
http://www.slimjet.com/chrome/google-chrome-old-version.php
then
go to Terminal and copy and paste this command:
cd ~/Library/Google
sudo rm -R GoogleSoftwareUpdate
Type in your Admin password to stop it auto updating.
This means that until Google sort out Chrome and its numerous issues with Chromecast and Mac it will not update to version 52 which is where I started getting issues.
As a sidenote, I found Casting with El Capitan was a pain so you can rollback to Yosemite if you desire.