MY TRUCK HAS HAD 3 INSTANCES OF THE BRAKES NOT WORKING CORRECTLY IN THE LAST 2 MONTHS. EACH TIME MY BRAKE PEDAL BECAME VERY DIFFICULT TO PRESS DOWN AND MY TRUCK DID NOT STOP IN THE MANNER IT SHOULD HAVE. EACH TIME THIS HAS HAPPENED IT WAS AFTER STOPPING AND PUTTING THE TRUCK INTO REVERSE TO PARK IT. THE BRAKE PEDAL BECAME HARD AND WOULDN'T GO DOWN THE WAY IT SHOULD. AFTER EACH INCIDENT AND PUTTING THE VEHICLE IN DRIVE THE SAME HARD PEDAL PREVENTED THE BRAKES FROM WORKING CORRECTLY GOING FORWARD. AFTER STOPPING, TURNING OFF THE ENGINE AND RE STARTING THE VEHICLE THE BRAKES WORKED FINE. I FOUND A BULLETIN ONLINE THAT GENERAL MOTORS PUT OUT WHERE A MECHANIC INSPECTION SHOULD BE PERFORMED TO CHECK IF ANY OIL WAS IN THE BRAKE VACUUM LINE LEADING INTO THE BRAKE POWER BOOSTER WITH THE OIL STEMMING FROM THE BRAKE VACUUM PUMP. UPON INSPECTION THERE WAS NO OIL FOUND AND MY MECHANIC PERFORMED AN OVERNIGHT PRESSURE TEST ON THE VACUUM PUMP ITSELF AND THE FOLLOWING DAY FOUND THERE WAS NO VACUUM LEAK DETECTED. THIS TEST WAS PERFORMED ABOUT 2 WEEKS AGO AFTER MY SECOND INCIDENT. MY 3RD INCIDENT HAPPENED THIS PAST FRIDAY 12/21/2018. MY TRUCK DID NOT STOP THE WAY IT SHOULD HAVE BACKING INTO A PARKING SPOT AND I WOUND UP HAVING MY TRUCK DRIVE INTO A CHAIN LINK FENCE AS MY BRAKE PEDAL AGAIN GOT REALLY HARD AND MY BRAKES FAILED. I AM VERY CONCERNED NOW THAT THERE IS A MAJOR DESIGN FLAW THAT DEVELOPED FROM A CASE OF POOR QUALITY MATERIALS USED IN THE MAKING OF THE PARTS OF THE BRAKING SYSTEM.