Why does my email exit to the list view when I'm trying to read it?

[AC Question]

Samsung S6 Active, Android 5.1.1.
When I get an email and click into to view the content, 80% of the time my screen kicks back to the list of emails, and then I need to reclick into the message. This sometimes happens 3-4x before I finally can read my message.
I thought it was just a weird thing I was doing at first, but now a colleague has told me his S6 does the same thing.