Issue with ‘sent’ in inbox

I’ve searched things up and apparently others have this too but recently I’ve seen that I have ‘sent’ as an indication on multiple people in my inbox. This is strange as I have never messaged these people and when I open the chat there is nothing there indicating I sent anything. I’m really lost I have multiple variations of this like sent yesterday sent 3 days ago and just sent I have this for 15 people none of them say seen and no one has responded to them. I’ve seen the theory that they are old messages being sent later but that can’t be true as I’ve never talked to these people.