Button 2 not working on controller

Hi I am having an issue with a master system 2 that i have just purchased. Basically, Button two is not working. Have tried and bought new controllers to rule that out. Continuity between pin 9 on the controller connecter is okay and pin 9 to resister R6 is also okay and leg 20 on the IC4 chip to R6 is fine. I have de-soldered and re-soldered the controller connecter just to ensure a good connection. Could the ic4 chip be dead? I really want to solve this for my master system 2

Thanks