What was found
(CAN) DEFECT: ON FINAL APPROACH FLAP WAS SELECTED TO 10 DEGREE. THE FLAP POWER CAUTION LIGHT CAME ON, MISSED APPROACH WAS EXCECUTED BUT FLAPS STAYED AT 5 DEGREE, FLAPS WERE OVERSPEED 2.5 KNOTS, QRA WAS EXECUTED WITH THE CB RESET. UPON RESET THE CAUTION LIGHT EXTINGUISHED, ANOTHER APPROACH WAS ATTEMPTED AND FLAP POWER CAUTION CAME ON AGAIN AT FLAP 10 SELECTION. MISSED APPROACH WAS EXECUTED AGAIN. ABNORMAL FLAP LANDING QRH WAS COMPLETED AND PLANED LANDED FLAPS. RESOLUTION: THE FLAP CONTROL UNIT WAS REPLACED, NO FIX. DURING FURTHER TROUBLEHOOTING THE CENTRAL DIAGNOSTIC SYSTEM CONFIRMED A PRESSURE LOSS DURING OPERATION. THE FLAP POWER UNIT PRESSURE SWITCH WAS REPLACED. SYSTEM CHECKS WERE CARRIED OUT WITH NFF. INSPECTION FOR FLAP OVERSPEED WAS CARRIED OUT WITH NFF. THE AIRCRAFT WAS THEN RETURNED TO SERVICE. (TC# 20190802012)