Couple options:
Order a a queen from a trusted source and kill the old queen.
Raise a queen from your gentle stock or put a frame of eggs in from your gentle stock, kill the queen, and knock down any queen cells that aren't from that frame - forcing them to raise an unrelated queen.
Or go through the hive and just kill the queen. Gentleness seems to be from the father side so simply having them raise a new queen, and hope she breeds with gentle drones, could be enough.
With that said, I have ZERO tolerance for hot hives because I don't want them raising drones.
Order a a queen from a trusted source and kill the old queen.
Raise a queen from your gentle stock or put a frame of eggs in from your gentle stock, kill the queen, and knock down any queen cells that aren't from that frame - forcing them to raise an unrelated queen.
Or go through the hive and just kill the queen. Gentleness seems to be from the father side so simply having them raise a new queen, and hope she breeds with gentle drones, could be enough.
With that said, I have ZERO tolerance for hot hives because I don't want them raising drones.