Texts Being Marked as Read, when I haven't read them

A

AC Question

I have a Sony Experia Z3v, and it just updated to Android 5.1.1 today. I noticed after the update that the notifications for my texts would show up for only about a second and then disappear, even if I hadn't check the notification yet. I played with all of the notification settings and nothing worked. Finally, I realized that as I receive the text message my phone is marking it as having been read right away, which is why the notification disappears. Anyone have any idea how to resolve this? I'm using the pre-installed Message+ and played with the settings for the app as well.