As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NON-REVENUE FLIGHT, DURING CLIMB OUTFLOW VLV OSCILLATED CONTINUOUSLY FROM CLOSED TO HALF OPEN. PERFORMED CABIN PRESS ERRATIC CHECKLIST. PRESSURIZATION RETURNED TO NORMAL ON STDBY PRESSURIZATION CONTROLLER. R & R NR 1 CABIN PRESS CONTROLLER IAW 21-32-00. LEAK & OPERATIONS CHECK & OPERATIONS CHECKED GOOD IAW 34-11-00.