I have a scene i export from Blender via glTF, and it seems that linked duplicates/instancedMeshes does some odd things, but maybe I am just missing something. I reproduced it in a PG;
The original mesh is the middle sphere, if you rotate the camera so the original goes out of frame the instanced versions wont contribute to the AO post effect. If you enable the bounding box in the inspector for the 3 objects only one bounding box will show at a time, depending on if original, instance 1 or instance 2 is in frame or not. So my thinking was that this ties in to how the AO behaves.
Is this a bug, or am I missing something? Do I need to “fix/freez” the instances or something ?