Dispensers drops shulker boxes as items if obstructed

Verification builds:
1.2.5.15 Retail

Summary:
If a dispenser is used to dispense multiple shulker boxes, the first box is placed (as expected) but subsequent boxes are dropped as items. This happens also if the dispenser's output is obstructed. In the Java edition, the dispenser won't drop shulker boxes if the output is obstructed in anyway.

Steps to Reproduce:

1. Place several shulker boxes in a dispenser

2. Activate the dispenser several times

Observed Results:
The first shulker box is placed, subsequent shulker boxes are dispensed as dropped items.

Expected Results:
It should place the first shulker box only, and further attempts to activate the dispenser will not work until the obstruction is cleared.

Screenshots/Videos attached: Yes

Notes: