Do you use multiple iOS devices or perhaps Messages on Mac? This bug has been driving me crazy for the last year at least, and I've noticed that it happens more often when I'm using messages on the laptop and phone.
Yeah, I have a Mac, iPhone, and iPad. The photo example I mentioned in another comment was definitely all on one device (I took the photo on my phone, sent it from my phone, and received the out-of-order response on my phone), but maybe even the presence of iCloud syncing is enough to screw it up.
