I have an integrated freezer which I inherited. It seems to stay on (continually freezing) so the thermostat would need replacing for it to function correctly. It looks like the freezer has already had work on the thermostat as there is some packing tape around the wire. It should be fixable with a cheap thermostat on eBay etc.
The model / no. is Schreiber APP6402 which seems to be the same as Hygena. It is well used and looks fairly old but certainly freezes fine. I'll upload photos soon.