As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: CLIMBING THROUGH FLIGHT LEVEL 300 WE FELT A RAPID CHANGE TO CABIN PRESSURE. CABIN WAS DESCENDING 4000 FEET PER MINUTE GREEN ALTITUDE LIGHT WAS ILLUMINATED. SWITCHED SELECTOR FROM AUTO TO ALTERNATE PER PROCEDURE. REMOVED AND REPLACED CABIN PRESSURE CONTROLLER NUMBER 1 PER AMM 21-31-01. OPERATIONS CHECK GOOD.