I've set up Chromecast Ultra and controller fine, everything says ready to go... I start playing a game and EVERY time, within 30-90 seconds the Chromecast will black out and say I need to re-sync controller. The controller is fine and still connected, I load the Google Home App and the Chromecast has crashed and I have to reset it.
Is this just a faulty Ultra? How do I fix it or get it replaced?
Try doing other non-Stadia activities with it to see if it behaves the same way.
For example, find a nice lengthy 4K video on youtube and cast it to your CCU and see if it misbehaves in the same way.