Please note: When I did this it was next to the world border, might not be everywhere!

While making an obsidian build in the corner of the nether (Next to the default world border) I decided to decorate the inside, everything: chests, blocks, even beds, worked perfectly fine, but on the X axis, when placing item frames, sometimes they will not go onto the block you try to put them on, but the block NEXT to it instead! Even if there is nothing to hang on!