Came across an interesting bug.
Testing Siri 3rd party integration, I sent a Whatsapp message through it. Before it is sent, it shows a preview: "here is your Whatsapp message to ABXY. Should I send it?"
In that preview, the message bubble with my text is actually not displayed, when it clearly should. It's empty inside the preview. I took a screenshot to document the bug, and, to my surprise, in the screenshot the message is displayed!
What makes this bug so interesting is that never before I've seen a screenshot show differently from what it's displayed, even when there's some graphical glitch going on.
iOS 10 with iPhone 6s+