As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, HYDRAULIC QUANTITY LEVEL STARTED SLOWLY DECREASING. ACFT RETURNED TO ORIGINATING STATION. FOUND SLOT CONTROL VALVE LEAKING. R & R PACKING AND O-RINGS IAW MM 20-60-0 AND 27-80-4. SYS OPS AND LEAK CHECKS GOOD IAW MM 27-80-0. SERVICED HYD SYS IAW MM 12-30-1. RAN ENGINES IAW ATI ENGINE RUN HANDBOOK 70.01. ALL CHECKS GOOD.