What was found
DURING CRUISE, AT FL350, NOTICED CABIN ALT STARTED TO CLIMB. CREW DONNED OXYGEN MASKS & STARTED DESCENT. PAX O2 MASKS DROPPED AT FL140. STANDBY PRESSURIZATION DID NOT WORK, F/O SWITCHED TO MANUAL. AFTER CABIN ALT RESTORED, F/O SWITCHED BACK TO STANDBY & IT WORKED. SINCE STANDBY & MANUAL METHODS NOW BOTH WORKED, CREW AGREED TO CONTINUE ONTO PHL. FLT LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY DECLARED. MX FOUND CABIN PRESSURE SELECTOR PANEL OUTFLOW VALVE OPEN/CLOSE SWITCH STICKS INTERMITTENTLY. REPLACED PANEL PER MM 21-31-00.