This fridge freezer is actually made by Beko but just badged up Blomberg.
The most common cause for this is the electronic control failing. Theres 2 in there. You have the temperture pcb inside the fridge behind the dial and then you have the main control board at the back behind the plastic cover.
When we get this fault we was told by Beko to replace both boards at the same time as it could be either. Most of the time this cured the fault.
But the odd time if it still carried on getting to cold then the fridge thermistor was the fault. Now this cannot be replaced as its foamed in at the back so theres no access to it at all. In this case the appliance will need to be replaced.
But most of the time new control boards cured this fault. So replace both boards and fingers crossed that cures it from there.