Bauknecht KGC2833/1 Flashing FastFreeze Light

I looked at a Bauknecht KGC2833/1WS today. The customer complained that the FastFreeze light was flashing. It is a 10+Yr old standard (non frostfree) electronically controlled fridge freezer. I checked the temps – both spot on. No excessive frost build up. The instruction book made no mention of a flashing the amber light. If you press the FastFreeze switch the the lamp becomes constant and the compressor started running sweetly. Can anyone tell me what this means? Apart from the fact that I have a panic stricken puss pot of a customer!