Since fridges are topical.....

Our single thermostat fridgefreezer was struggling to keep the fridge at
4degrees even before the hot weather, but now it's not coping properly at
all. Freezer is fine!

I get a coating of ice about 1.5cm thick on the back inside wall of the
fridge - so I have to hack it off every couple of months .

Is this proper - not sure if this is impiring performance or part of it -
or is it a clue to what's going wrong?

cheers