Good morning my name is ***** ***** I will try and assist you today.
Just reviewing your specific models specification.
The most likely cause is a build up of moisture in fridge freezer.
Since you have already defrosted it and its reoccurring this is clearly a reoccurring fault.
If the door seals are fine, make sure it makes good contact all around the appliance to rule out an issue with the door not being square.
I would then look to check the condensation drain at the back of the fridge, and see if this is blocked, there should be a channel which takes away the moisture in the fridge, and expels it into the evaporation tray at the rear.
This sounds like the appliance isnt level, as water (moisture should run from top to bottom), check with a bubble level and adjust the feet as required to ensure its not leaning to the right. There should be a slight lean backwards on the back wall which should help it run down into the condensation channel.
If your still seeing the a build up of ice, it may be a thermostat fault, where the fridge is varying in temperature eg cooling to -1 degrees, then warming up to +10 before the thermostat kicks in to cool a again, this would increase the amount moisture on the back of the fridge, the best way to check is place a cheap fridge thermostat in the fridge and check it every hour of the course of a day and see if it swings dramatically.
With this model it is rather difficult \ fiddly trying to get the cable from the control board to where the thermostat is located, as the nature of them being integrated means you dont often have access to the channels the cables run through.
You can purchase a replacement thermostat for around £35 from spares online firms such as this one here, if you provide me your postcode I can recommend an engineer in your area who can fit it for you, and rule out its a control board fault before replacing the thermostat.