I bought this small fridge freezer about a month ago to replace an older model (MUR4892MB) which I had accidentally punctured during defrosting and all the gas had escaped. I was pleased at first as it seemed to have a more separate sealed freezer compartment. The older one had a habit of freezing the contents of the fridge meaning I could only use the lower shelves for cooling beer and milk etc. However, now that I've owned the newer model for a few weeks, I find the same issue occuring. How ca