Hello, my name is ***** ***** I will assist you with answers to your problem. I am not on here constantly so kindly be patient whilst awaiting answers.. I will return.
You need to defrost your freezer and remove the panel at the rear... Check the drain-hole behind the panel for blockages.. Pour some hot water down the hole to help clear any blockage until you can see the water flow away with some consistency.
This needs to be done over a period of 24hrs... You should then dry all parts and refit.
Once you have done all this you can then restart the appliance.
this should have cured the problem... However, keep an eye on the appliance, if it happens again over the space of a couple of weeks you'll need to change some parts...
You can come back to me thereafter for a list of those parts if you find it necessary... and I shall then give you further advice on fitting them