Another interesting Bug appeared!
This time, Minecraft crashes.
I'm going to explain this with pictures again...
Step one, create a Block (with container), a GUI (with some input slots, in my case there are two) and a Procedure (to open the GUI):
The Block with Inventory selected (Everything else is not edited):
The GUI is bound to the Block:
The GUI can have a few input slots (I created 2 random placed slots):
And finally the Procedure for opening the GUI:
Now run the Mod in the client environment and as you can see you can open the container GUI:
Now switch into Spectator mode:
And open the container Block, as you can see nothing happens, minecraft does not crash:
Back to MCreator... Now change the Size of the inventory to something smaller than 9 (I changed it to 8):
Back in Minecraft... After you click on the Block, Minecraft chrashes:
I attached this workspace down below, so you don't have to create the mod elements.