read-receipts switch back to delivered??

Why are my read-receipts changing back to delivered?

I am having this issue in iOS 10 on both iPad and iPhone. Very annoying. And its not due to the other person changing any read-receipt settings. I tested it out with my father. Screenshot every step.

So first my message was read and the read receipt showed it...

That's normal. Then I looked again at 4:57 pm, and it went back to "delivered"

Then even after a reply from my father, it still showed "delivered." Note that my father did not change his read-receipt settings.

Finally, after a hard reset of my iPad, the read receipt showed up again.

AND this whole thing occurred the same way on my iPhone as well.

I don't think this is a problem with my ipad or iPhone. I've done resets, erased settings, etc. It seems to be a bug in the iOS.

HELP!!