As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BLOCK TURNBACK PRIOR TO TAKEOFF DUE TO HYDRAULIC QUANTITY LOSS. CHECKED HYDRAULIC RESERVOIR, FOUND FULL; CLEANED CONNECTOR AT HYDRAULIC QUANTITY TRANSMITTER IN ACCORDANCE WITH M/M 20-50-1; CHECKED HYDRAULIC QUANTITY, FOUND NORMAL READING.