This is happening to all my shirts, too, but no one else's in the family, so it's not the wash machine. Thought it was the seatbelt on my car that we recently bought. Still haven't ruled that out. Then thought it was the clip I use for my swipe card at work, so I moved it and it's still happening. For right now it appears to be the zipper on my jeans rubbing against my shirts when I sit down and it exposes the zipper pull, but it's so random. Ruining shirts left and right gets expensive.