Freelander 2 HSE Auto - Parking sensor failure

Hi All, I have a Freelander 2 HSE (57). I knew when I purchased the vehicle the parking sensors did not work. A loud beep to let me know there is an issue. I had the car on the diagnostics and the front right sensor shows an issue. My problem is why have ALL the sensors failed both front and back, Surely if its an issue with the front right then the reverse should still work. PDC light flashes when pressed just for info. Many Thanks.

If one parking sensor fails, it renders the whole system inoperable. Changing the failed sensor will restore it's function