Some people obsess over exposition coming from characters and dialogue. And when done well that can be amazing!
But if it feels unnatural, like characters are explaining things they should already know. Well… it becomes problematic.
It’s okay to have clarifications made by the narrator. The narrator is there to be a guide, a helping hand, and I think people are scared away by all the writing advice saying not to do this.
But you can do this! As long as it’s not excessive, I’d much prefer character’s who feel real and like they live in a real world, accompanied by exposition, then character’s who feel like exposition machines.
Remember to use your narrator! And allow your character’s to know stuff, especially in later books.