When opening the Iron Furnace GUI it just... Breaks Minecraft, forcing you to close it.
The Electric Furnace is using the brewing stand GUI- And it let me take 12 rubber from the Brewing Stand GUI when I opened it.
...Second one is kind of funny, tbh.
Might come across more in a bit.
Edit1: Cannot break said Electric Furnace with an Iron pick... Keeps coming back. Then disappears and corrupts the spot it was in. Placed wood, cobblestone appeared.
Oh wow. Everything is getting corrupt now. Things are duplicating, being removed. Inventory is becoming corrupt.
Edit2: Server managed to fix the inventory thing on it's own- and the spot where the Iron Furnace was (Lost the furnace somewhere along the lie as well).
Edit3: Added that it's SMP where I'm testing stuffs.