So I made this character, or half of it while mirrored along X, as you can see here
But when I apply the mirror and try to unwrap the UV I get this
Notice how the mouth is different on one side, I don't understand it as it should be exactly the same. Everything else unwraps perfectly, and the only thing I did was work on that part of the mouth with the mirror invisible so I could see better from the inside. But I've looked at it and it is definitely the exact same mesh on both sides. I've tested it a bunch of times now, same result every time. Mark seams, apply mirror, unwrap, and the mouth area is always wrong. Any ideas to why this would happen?