Exclamation Point in Triangle in Messages

[Seekingone]

I have a Pixel and there's an exclamation mark in a gray triangle to the right of a couple of my contact names when I go into "Conversations" under the tab "Messages." I've gone quite a ways back to see if some of the messages didn't send, and didn't see anything. I could spend hours going through all of them.

 

[Trees]

Not something I've seen. Usually its a "failed to send" or similar indicator/message due to poor signal in my experience. You could try Settings\Support\Phone or Chat option and see if Google Support has some ideas.