It is a anonymous bug/glitch that happens when making a shop you'd have to ask Justin about this one cause he doesn't even know what causes this bug/glitch
IS there another sign on the same block? That's what causes it for me, you can replace the original sign(If not shop sign) after breaking it off.
Fill in the glitches spot with a block the log out log on then destroy it then try to place the sign and if tar doesn't work keep trying
If you're placing the sign adjacent to another shop sign on the same block, that won't work. Two shop signs can't touch at the edge. Edit: Well my slow phone typing made this post moot.
