If the immersive environment is fully open, then an immersive space is closed right after attempting to open it.
The issue specifically impacts a mixed immersive space which replaces the immersive environment while the immersive environment is at 100%.
This issue does not occur if immersive environment is any less than 100%, or if the immersionStyle is .full, or if immersiveEnvirionmentBehavior is .coexist.
This can be reproduced in the template for an immersive visionOS app by removing the line .immersionStyle(selection: .constant(.full), in: .full) Then run the app and open the immersive space, and the space then closes after attempting to open it.
I’m using visionOS 27.0 beta 5 and Xcode 27.0 beta 5.
I've submitted feedback as FB24353599
Video of the behavior: https://youtu.be/wafDXRZVyog