What was found
WHILE CRUISING AT FL 150 THE CABIN PRESSURE STARTED TO FLUCTUATE FROM FULL RATE OF CLIMB TO FULL RATE OF DESCENT. CREW STARTED AN EMERGENCY DESCENT AS CABIN PRESSURE STARTED TO CLIMB UNCONTROLLABLY. AIRCRAFT REACHED 1000 FEET EXPEDITIOUSLY AND THE MAXIMUM CABIN ALTITUDE EVER REACHED WAS 8000 FEET. COMPLETED COM AND LANDED WITHOUT FURTHER INCIDENT AT LSE. MAINTENANCE REPLACED THE PRESSURE CONTROLLER AND OUTFLOW VALVE AS PRECAUTIONAREY MEASURE. SUSPECT A/C TO BE INTERMITTENT BETWEEN AIR MODE AND GRND MODE. NO BITE ACCOMPLISHED.