I have recently noticed that when I am using my device (OnePlus3 - 7.1.1) and a new message comes in, the actual context of the message is not displayed if an earlier message is not acted upon first. This also applies to any Textra messages pushes to my smartwatch, and any other apps that have notification access. Instead of the contents of new message, it just says "2 unread messages" (or 3, etc). This isn't very helpful if multiple messages are coming in from the same contact.