I had a funny one last week
The user is complaining that all there data keeps getting deleted.
So I watch them, they click the "override totals" checkbox, which spawns a message asking if they want to delete the existing data, Yes, No, Cancel.
And without reading it, they click Yes, and then say "see, all the data is gone, make it stop doing that"
So I have to show them that if they click No, that doesn't happen, they didn't even read the message. And this isn't just one person, around 30 people have had this issue.