My straps do the exact same thing! I really don't mind, though. I'm usually a perfectionist and I have OCD tendencies, but for some reason, the imperfections on the PSMs don't bother me. I think it's because they bag themselves are so tiny. If I had the bigger sizes and the monogram was misaligned, it might bother me since it would be more noticeable. The mini is cute enough for me to look past it!
Anyway, I think if you really wanted to return yours, you should do it sooner rather than later! You might have to wait to get it replaced, though.