When you break Chest, Sign, Enchanting Table, Ender Chest, Skull, Trapped Chest and Banner in the debug world mode. It's not reload model.
Comments 3
It clearly does. Dinnerbone's comment from MC-59091:
Debug world is for debugging. It will not be officially supported for features and play. Bugs will happen in things we don't intend to use it for, and they will stay.
Any bug involving breaking blocks in debug mode is invalid, as you are not supposed to touch anything in a debug world.