Zanussi ZX99?

Hello
I have a Zanussi ZX99 fridge freezer - that periodically (almost every single day) is 'beeping' and the three lights flash on and off. The only way to stop is to power off then back on again.... this is a short term fix however and within a few hours - it starts again.... nothing noticeable wrong with either fridge or freezer as both seem to maintain a regular temperature. No ice evident and I did attempt a defrost for 12 hours last week - but no water pooling confirmed no ice present...

I have read this could be an NTC fault - (and for £30 it could be worth a go). ? If so, how do I go about replacing? Do I remove the back panel and look for a wire similar to that I will replace? Or is it a little more involved than that?

Any help would be greatly appreciated..... thank you.