How to stop water forming at base of fridge. ?

We have a Schreiber Model APM6125 under worktop fridge with small freezer section where small amounts of water are forming under the plasic containers. The small hole at the base through which I believe any moisture should go and then evaporate is clear. A thin layer of ice is forming on the back panel of the fridge. The temperature has been adjusted but does not seem to make any difference. There is air flow at the plinth area.Any ideas please?