Why does my hotpoint RLA50 larder fridge keep freezing back wall and contents

Lots of possibilities. The temperature set point may be set too cold. You should set the temperature for around 40 F (4.4 C).

If that's not the case, the damper that controls air flow throughout the refrigerator may be stuck or otherwise not working properly. The defrost timer may have failed and it's not periodically defrosting the wall.