As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT CRUISE ALTITUDE IN BOTH AUTO AND MANUAL PRESSURIZATION AT ALL FLOW SETTINGS, CABIN CLIMBS AND DESCENDS UP TO 700 FPM AND WILL NOT STABILIZE AT CONSTANT PRESSURE LT MANIFOLD PRESSURE FLUCTUATES 3 PSI IN CRU.FOUND LT FLOW CONTROL VALVE TO INTERMITTENT/INOP IN ANY POSITION ABOVE MIN FLOW DEFER VARIABLE RATE FUNCTION PER MEL 21-40-1. R&R FLOW CONTROL VALVE IAW SMM21-55-5. CHECKED OPERATION OK.