As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MADE AN UNSCHEDULED LANDING AFTER DEPARTURE, PILOT NOTICED A CAS MESSAGE "ROTOR BRAKE". THERE WERE NO ADVERSE INDICATIONS THAT THE ROTOR BRAKE HAD ACTUALLY INADVERTANTLY ENGAGED. MX INSPECTED THE ROTOR BRAKE SYS AND MADE ADJUSTMENTS TO THE SENSOR THAT CALCULATES THE DISTANCE BETWEEN THE BRAKE DISK AND PAD. ACFT WAS RETURNED TO SERVICE.