Probably a bad regulator. You'll need to pull the door card to be sure. The top tooth is commonly worn since there is no electronic stop on the system and it is the most used window.

They can be repaired if you choke on the price of a new one. Requires welding and fitting but doable.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now