Versions:

Mod version: Built from source, latest commit: 8be6262 - view
Forge version: 1.11-13.19.1.2188

Details:

Double chests drop items on the half with no lock entity.
The end of a double chest that doesn't contain the lock entity is breakable, and will drop it's contents when broken by a player. Break event needs to be cancelled for adjacent inventories affected by the lock system.

Fixed in 0.4.2-pre1