Hello all, this is a crucial bug fix that I discovered myself while testing the plugin.

The bug was that if water is placed on the supporting block the "Shulker Box" is attached to, it will not drop a Shulker Box.

This bug has now been fixed and the Shulker Box will be dropped.
You can still place water around it and on top of it, and it will remain there.

Unfortunately, due to the limitations of Spigot/Minecraft internals in 1.8, there was no way around it, but to break the Shulker Box.