As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE A HYDRAULIC SYSTEM PRESSURE AND FLUID WAS LOST AFTER GEAR WAS RETRACTED DEPARTING IAH. FUEL WAS DUMPED AND THE AIRCRAFT WAS RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE RT MLG LOCK SEQUENCE VALVE LEAKING. THE VALVE WAS REMOVED AND REPLACED IAW MM 32-32-31. LEAK AND OPERATIONAL CHECKS WERE GOOD IAW MM 32-32-0.