As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5145 - THE PILOTS REPORTED THAT DURING CRUISE THE VACUUM PRESSURE WAS READING AS LOW AS 3.5 AT FLIGHT LEVEL 220. MAINTENANCE REMOVED AND REPLACED THE VACUUM REGULATOR VALVE IAW B1900D MM 37-00-01. THE OPERATIONAL CHECK WAS GOOD.