Here's my finding: It works when I put #Preview {} before the #Playground {}. Been shaky though. If I still see it, I can remove derived data and restart the Xcode. Works most of the time. Not sure if this is acceptable, but this is the life of bleeding edge beta. Hopefully next version can be better.

Additional FYI: I was going to re-image the OS, but noticed that Beta 3 works fine. (That means it's not the OS issue, right?) Currently using beta 3, but keeping on a lookout for any similar issues from others. So far, none. I'm using MacBook Air M3 with 24GB RAM.