Dave,
Thank you.
I did think that it was an odd statement for the engineer to make but apparently it was based on advise from Electrolux (the manufacturer of AEG) freezers. The engineer did test all the components and found odd readings on the compressor (it has an inverter compressor). At times it read fine but at others it dropped. The cost of replacing the compressor is astronomical and not economical at all. I will endeavour to find a new engineer or a new freezer!!