From another site
the button is a super freeze option -what it does is runs the motor constantly without cycling to freeze down quicker ,it bypasses the thermostat ,used when you might do a big freezer shop ,you normally hit this switch for a couple of hours -
however if the button is left on constantly it will cause problems as its bypassing the stat and running the motor too much and could burn it out
unplug your fridge let it defrost ,plug in again and let it start cycling without that switch on ,if you still get problems it may be too late for your fridge