If an inventory (so far only happens with Trash Can, not much testing though) is shift-right clicked with a toolbox in hand, the toolbox is set to a wrench, and then the block is activated. If the block either consumes the wrench (in example, a barrel) or opens an inventory, the wrench is left behind in the players inventory, without the toolbox rendering.

However, if the player now right clicks the wrench, it will become a toolbox. If the player opens the inventory screen and picks up the wrench and then places it, the toolbox will be lost (forever).

With barrels (and other blocks which consume items) it is possible to duplicate any wrench by shift right clicking the barrel. The wrench is consumed by the barrel, but the moment we stop clicking, we return to the toolbox, which still has a wrench.

The dupe bug is fixed (I already thought of this and added a check if the stack was set to null, but forgot to also check for a stacksize of 0).
I can't quite figure out why the client does show the right item, but it seems to be fine after picking it up (I haven't seen it disappear yet).
One more bug, for some reason item damage isn't showed correctly (using electric wrench), but I can also not find out why :(

The item is shown incorrectly after shift right clicking a trash can.. have you tried that? And by picking it up I mean moving it to another slot in the inventory.

By disappear I mean that the wrench that was equipped is left behind, the toolbox vanishes.

Fixed