So I was playing around in a creative map, and I was building a giant robot, I switch to cobblestone at the same time as I place a stone brick, and it shows I’m holding cobble, but i have stone brick equipped, so I start building, and I'm not paying attention, and then an entire part of my build was the wrong block. Very annoying bug that can ruin builds. (P.S, I am using a mod in the screenshot, but it only adds a few blocks and changes a few textures, no code changes.)