As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR RETURN DUE TO A PRESSURIZATION PROBLEM, CABIN ALTITUDE EICAS. FLIGHT WAS AT FL360, THEN DESCENDED TO FL100 AFTER THE CABIN PRESSURE CONTROLLER AUTO 1 FAILED. DECLARED AN EMERGENCY. DURING DESCENT, FLIGHT MAINTAINED FL100 CABIN ALTITUDE. IT WAS NOT A RAPID DESCENT & MASKS DID NOT DEPLOY.