AEG Arctis Freezer fluctuating temperature – evaporator fan?

My freezer started behaving erratically, warming up to -4 with alarm beeping and then sometimes going back down to -18. Eventually it stuck at -4/5. On dismantling it was clear that the evaporator was completely frozen. I emptied the freezer and allowed it to defrost completely. I have left it empty and its temperature is now fluctuating between -18 and -11. The evaporator gets quite frosty and is then automatically defrosting.

The evaporator fan seems not be working. I cannot find a door switch so am I assuming this is possibly internal and am unable check by direct observation. However, I have checked whether or not the fan is turning by leaving my phone in the freezer and videoing the fan with the door closed.

The videos show that the fan sometimes gives a little “kick” and moves about a quarter of a turn when the door shuts, but then goes no further. On other occasions it does not move at all. If I then push the fan blade on a bit it may give a kick next time the door is closed but then nothing. I’ve checked it at various temperatures.

I suspect that the fan not turning is a possible cause of the poor cooling. I’m guessing that this could mean a faulty fan, or a fault somewhere in the system that tells it to turn (although untrained instinct tells me that if it was the latter it would perhaps not be moving at all).

My dilemma. Is it worth spending £55 or so to buy a new fan in the hope that this is all that is wrong?Or is the likelihood that the fan not turning is just a symptom of something else wrong (beyond my abilities) and I will then be up for even more expenditure? The freezer is about 7 years old and we had to have the two control modules replaced a couple of years ago so not keen to go on throwing good money after bad if it makes more sense to replace the freezer altogether.

Many thanks in anticipation