An uneven floor
If you go with a floor pattern, you should commit to it and go all the way. If all the tiles are facing one side, you can’t just have one tile placing the other side and hope no one would notice. In fact, that’s pretty hard to miss. Just this one little tie, the odd one out, standing on its own against the world. Poor tile.
What makes this even more infuriating is that this mistake – like almost every mistake on the list – should be so easy to fix. I mean, perhaps not now, but one the tiles were just applied the the glue was still fresh, it shouldn’t have been too hard to remove and adjust. But no – as it turns out, some people just don’t care.