Summary
Using the SimpleAR scene when I navigate in Game view using AR Simulation, if I click the Pause button then Game view will become entirely black except for Point Clouds.
After clicking the Resume button, scene geometry re-appears along with previously discovered planes, but no Point Clouds are visible.
No further planes can be discovered via navigation (right-mouse + WASD in Game view).
The Reset button does not help; I next need to exit Play mode, then re-enter Play mode before plane discovery works again.

To See the Bug
Open the ARF Samples project in the Editor.
Open the SimpleAR scene.
In Build settings, select desktop platforms.
Enable XR Simulation in Project settings.
In Scene view, use the AR Simulation overlay to select the biggest office simulation environment.
Enter Play mode.
Click in Game view to give it focus.
In Game view, click the Pause button.
In Game view, click the Resume button.
Exit Play mode.
Note the error in Console; this is the bug.

Configuration
2021.3.0f1.2 (2021.3/staging 6eacc8284459)
MacOS 12.0.1, MacBook Pro (15-inch, 2019), 2.4 GHz 8-Core Intel Core i9
AR Foundation 5.0.0-pre.10 (f6569c5)