Brandt Apollo fridge freezer sounding alarm?

My Apollo fridge freezer is having some cooling problems so I followed the advice on here and defrosted it the hard way (pulling panel off inside freezer etc)

It still isn't cooling very well and when I turn the fast freeze on, the yellow light and the green light flash rapidly and a buzzer sound intermitantly buzzes in time with the flashing of the lights. Does anyone know what this means? It's not in the manual. Low gas pressure? Thanks

David Valentine
February 2009