Reproduction steps:
1. Open the attached "IN-136314_ARAnchor_FIX1.zip" project
2. Open the “Assets/Scenes/ReproScene.unity” scene
3. Enter Play mode
4. Wait for 3 seconds
5. Observe the Console window, look at the last log

Actual result: You will see an error log with "BUG REPRODUCED" in its title
Expected result: You will see a log with "anchor.pending resolved after x frames" (x can change depending on environment)

Reproducible with: 6.3.0-pre.2, 6.5.0-pre.2 (6000.4.0a1)
Not reproducible with: 6.3.0-pre.1 (6000.4.0a1)

Reproducible environment: Windows 11
Not reproducible environment: No other environments tested

Workaround: In Editor XR Simulation, avoid relying on “ARAnchor.pending” becoming false and use a different condition such as “trackingState” or skip the pending check in Editor only logic