Hmmm...
Does it
feel flat? Sometimes the finger will find what the eyes can't see. If you feel any undulations or bruising, a light wipe on a stone might help it.
I doubt the pivot will have galled, so the only other thing I can think of is debris between the blades in the pivot area. If you (or someone you know) has an ultrasonic cleaner, it might be worth giving that a go.
Failing that, I think you're right - it's warranty time.