I can confirm this same issue is also occurring on my device. I am using visionOS Developer Beta 2.5, and can reproduce this issue by using Apple's Sample Code Building local experiences with room tracking. If Apple could confirm that this is either; A bug in the ARKit World Anchor persistence or expected behaviour, that ARKit World Anchors must persist at least one anchor that would be very helpful for us!

I can confirm I also have this issue on VisionOS 2.5. Using the sample code https://developer.apple.com/documentation/visionos/building_local_experiences_with_room_tracking you can replicate the issue. I have also submitted this to Feedback Assistant.

After multiple reboots, the issue has resolved itself and the attached code now works as expected with no build changes. When present the issue was present for several hours across multiple reboots before resolving. I will update again here if it reoccurs!

Reverting to Beta 3 also does not work with this sample.

Reverting to visionOS 26 Beta 2, the sample works as expected!