It’s best to troubleshoot issues individually, so I have split your post into it’s own thread.
Can you please provide some more information regarding your setup + chromecast models by using this thread as a guide?
Downgrading versions of Roon is not supported but we can certainly look into this issue on the new build and investigate what is going wrong.
As I mentioned in the thread I split you from, I am using two Chromecasts (Ultra + Built-in TV) on my end, so I believe this issue could be environmental.