Periodic tripping of earth leakage switch. Our Kelvinator Impression Series 640L side by side

Question

Our Kelvinator Impression Series 640L side by side fridge freezer (approx 10 years old) has started to periodically trip the earth leakage switch. It appears to be possibly during the defrost cycle, however I'm unsure of this. I wondered if it may be thermostat, defrost part, or a fan or element problem. Could only happen on New Year's Day! I would appreciate any suggestion or advice you could give. Cheers - Happy New Year.
Ando.
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