SCHREIBER APM6214 Freezer – not freezing?

Hello, my mum in law defrosted her freezer.
Fine, shouldn’t make any diffeence.
But she used a steamer to help clean it out (OUCH!).

Now even though it’s on super freeze, the red light is still on and it’s hardly cooling right.
The top shelf has ice on it, but food in it is not freezing.
Door seal looks fine, I was wondering if it’s likely to be the thermostat?

I suppose I can remove it frominside her units and replace that easily enough, it’s if it’s lack of gas etc that might cause a problem.

Any suggestions.
Thank you,
mattylad.
P.S. have emailed this site for thermostate replacement price.