When you use the dispenser to launch the shulker box at the height limit, depth limit, or horizon limit (in old worlds) of the building, the shulker box will disappear directly instead of becoming an item or staying in the dispenser.
(I know that almost no one will do this deliberately, it's so boring )
- Travel to the height limit
- Place a dispenser facing upwards at the height limit
- Put a shulker box containing items in the dispenser
- Activate the dispenser
Here, the shulker box will not be placed, but will also not stay in the dispenser.