When a chunk is updated every tick, the AO disappears,
When not updated at every tick, the AO does not disappear.

How to reproduce

1. Open and close a shulker box and watch the shadow (it should not change)
2. Now place two observers facing into each other in the same chunk
3. Now open and close the shulker box and watch the shadow (it disappears when open and reappears when closed)