I don’t think a user manual will help though if it’s defrosting, if it’s a frost free unit, try a complete defrost for 48 hours to clear any possible ice build up, apart from that you may need an engineer to check it for you.
Check the repairs@ link below should the need arise 😀
I have the same freezer. It sounds like the programmer inside is spending too long on defrosting. This is a device within the top of the freezer which should defrost the freezer every 15 mins per hour (or something like that). We had a faulty one that didn’t de-frost which resulted in excessive ice formation. The part was available when we had ours repaired (ca 12 months ago).