I have heard of this once before, on another forum. Out of curiosity, did they both come in the same pack? I'm not sure if the other person's did or not, but it would be interesting to know. It's not a common error really, I would say to check if they were fake but the fact that it's happened to someone else as well drastically narrows those odds. The weird thing about this error is that there are two cards involved, I can't even think of another instance where it wasn't just a one-card error. I would suggest to keep them for now, the set is still fairly new and I'm sure this misprint will come to light sometime soon.
For the sake of everyone's curiosity, do you have photos of them you could post?