As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DESCENDING THRU FL180 AN UNCOMMANDED EXTENSION OF GEAR WAS EXPERIENCED (GEAR DID NOT FULLY EXTEND) GOT UNLOCKED LIGHT THEN GEAR RETRACTED. - TROUBLESHOT AND FOUND HYDRAULIC MANIFOLD DOES NOT HOLD PRESSURE. REMOVED AND REPLACED LANDING GEAR HYDRAULIC MANIFOLD ASSEMBLY IAW CESSNA 750 MM CHAPTER 32-30-02, OPS CHECKED GOOD.