I can't spot what you are calling a miistake, however, if you put the quilt away overnight and it still bothers you in the morning, take it out. My daughter wanted a charm square quilt when she went to college and she wanted each square to be different. However, when I was quilting it, I noticed that two squares were the same, if she has found them, she's never said a word, and I'm sure your son won't either. By the way, I love the black and red fabrics, it's a beautiful quilt.