Hello!

This update fixes a bug with Dispensers, the bug occurs when a Dispenser and Piston are activated at the same time and the Piston breaks the Shulker Box, it caused the Shulker Box item to lose its data, due to how Minecraft works internally, this has now been fixed, although this is an edge case and does not happen often, it is strongly recommended you update to this version or newer.

And for developers, you can now cancel the placement of Shulker Boxes via BlockDispenseEvent #setCancelled()