I fixed this in at least one non-controller setup with: "no ip igmp snooping" and "no bridge-group 1 port-protected"  on the AP. The problem is actually with multicast and wirelessdevice-to-wirelessdevice communication. They just chose the worst poss...

apparently chromecast requires upnp to be enabled at the router. If you  keep your eye open during the installation, you will see an error when  joining the network, that leads to a web page that makes this clear. I  am attempting to open a ticket w/...