I have an Attacker pilot II at 2 stars. Game claims he needs 1600 exp to get to 3 stars. Screen above shows exp gain from a battle and claims he got 3 stars in a single match.
After that battle, back in main menu, my pilot levels from 2 stars to 3, despite game claiming he gained 13k exp.
Not the first time this happened, just the one I bothered to take a screen of.