Sorry for the delay in getting to your question, Do you still need help on this?
If so then could you post the model number please.
Ok if the hole is clear and the water is draining away fine then we know its not a blockage in there.
So if the drain gutter is forming ice and freezing over then im afraid this is an insulation fault. The foam insulation behind the liner breaks down and this causes moisture to form in the gutter and freeze up like this.
Im afraid when this happens theres nothing that can be done as its all foamed in at the back so theres no way of accessing it or doing anything with it.
Now this doesnt stop the appliance from working it just causes the ice to build up like this and can sometimes leak water from the bottom. So it just turns out to be an anyoning fault rather then one that stops it from working.
Sorry its not good news but this is a fault we do come across on now and then. So as the gutter hole is all clear and it keeps freezing up in there then it will only be down to a break down in the insulation in there.