What should I do ?
iPhone 5s, iOS 10
Ask the app developer. That is NOT the Apple Messages app. It's a 3rd party app.
Is that Facebook messenger? I've seen quite a few users experiencing the same thing when the attach anything (photo, voice message etc).
Facebook Messenger updated on the 13th. If you don't have the latest version, update from the App Store, if you do, then Facebook will probably be pushing another update out soon.
What should I do ?