I have had this issue happen regularly now on 2 games zombie army 4 and AC Odyssey. I play flawlessly for around 15 min then the screen goes black for a second or 2 then comes back but when it does the game lags real bad. There are about 4 secs between controller input and game movement. Oddly the audio seems to be near enough inline with inputs it's the video that's out. The same issue has happened once or twice with pubg but certainly not regularly like the above games - AC being the worst culprit.
If I exit game return to stadia menu and restart game the issue persists immediately but if I shut stadia down then start back up and load up the game I'm good to go for another short play session.
I play on Chromecast ultra with Ethernet and my speed is around 200mb. When I press stadia button on controller the connection reads as great and I can play in 4K.
I use virgin media as my provider and did their online test of my connection and router and all is good. Other devices at home have no noticeable issues.
Anybody had similar issues and found a solution?
For anybody that has a similar issue my Chromecast was behind a unit and got little airflow and I think this caused it to overheat I have moved the unit out a bit now and I'm now hassle free. Hope this helps someone else.