As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SFO INFLIGHT T178/21MAR - CREW REPORTED RIGHT HYDRAULIC FLUID LOSS. RETURNED TO SFO AND LANDED WITHOUT INCIDENT. FOUND RIGHT WING INBOARD NUMBER SEVEN SPOILER ACTUATOR NUT BACKED OUT WITH LARGE FLUID LEAK. REPLACED NUMBER SEVEN SPOILER ACTUATOR. SYSTEM GROUND CHECKED NORMAL OPERATION.