iMessage reverting from "read" to "delivered"

[Jaggedfel]

Over the last few weeks, I will send an iMessage to my wife. I get a read receipt when she reads it. A few minutes later, it will change back to "delivered". She has always left read receipts on. This has just started recently. It only happens when I send a message to her, no one else.
Has anyone else seen this, or know what causes it?

 

[J. A.]

Welcome to iPhone Forums, Jaggedfel!

This seems to be a bug which occurred with the update to iOS 9.3, and hasn't been fixed yet. So if your iPhone has 9.3 or 9.3.1 installed, it's possible that it's affected as well.
I've read somewhere that restarting the iPhone helps.

You could contact Apple Support and let them know about your problem, or send feedback:
Feedback - iPhone - Apple