Samsung Fridge displaying wrong temperature

I have a Samsung RL42HGSW, which I had replaced a faulty thermistor 8 months ago. It worked fine until these days, until another problem appeared: it displays the wrong temperature in the LED panel, however, if I unplug and plug it again, it shows the correct actual temperature, and, it starts to cool down to the temperature I’ve set (3C)(37.4F). Today, I’ve left it to work and see what’s going to happen without replugging and it started working though you can see condensation on inner walls of the fridge denoting that temp is much more than displayed. When it started working, I replugged the fridge then saw temperature 12C (53.6F) of fridge and 4C (39.2F) of freezer. Freezer’s temperature set is -20C (-4F).

Just giving a restart, unplug and plug, it fixes the problem for a day, then it returns again. What could be the issue this time? Probably defrosting issues (but I don’t think because it is actually able to cool down, just doesn’t know when to cool)? Or anything else? Thanks in advance.