Liebherr CUN3913 -1- 168255: Urgent weekend problem!

We have had the Liebherr CUN 3913 for just over a month. Last wednesday we noticed that the freezer contents were defrosting. The top shelf was soft,second shelf almost as soft,third shelf only just frozen and bottom shelf still frozen. Called Liebherr, they sent out Coolplus, who came on Thursday. The engineer tested everything, found no fault except that the freezer was probably frozen up behind the backplate preventing air from circulating. Told us to defrost the machine for 36hrs and restart. He did say that it should be possible to see the fan in the freezer coming to a halt, with the top drawer out, if you looked quickly on opening the door,(which automatically switches the fan off). The fan did not appear to be moving, although we looked several times together. My question is that now we are restarting the machine should the fan be working in the freezer section, when the power is switched back on? At the moment with the power on, the freezer green temperature light is flashing and so is the (red) alarm button, but I have been unable to see the fan moving at all. Is the fan faulty? We have the freezer Superfreeze button on. The only discrepancy with the instructions that we have noticed is that there was never an alarm sound to indicate a problem with the freezer temperature rising. Obviously I am not keen to fill the freezer with replacement goods until I am sure it works! Sorry for being so longwinded.