Observers aren’t activated when items are placed onto or taken from shelves

The Bug:

Observers aren’t activated when items are placed onto or taken from shelves.

Steps to Reproduce:

1. Place down a shelf and an observer adjacent to it.

2. Place some items on to the shelf and observe if the observer activates.

3. Take some items from the shelf and observe if the observer activates.

Observed Behavior:

Observers aren’t activated.

Expected Behavior:

Observers would be activated.