I do not know how to input the picture but maybe it will happen for you. It is where the original block starts (The random colored one when you click create) Overlays the new design.
If you place a block and it doesn’t show up that means it glitched, that happens to me too. Even tho it’s stored in the game files. That’s why reloading places it back. Just remove it or use it and go on with the game.