Hello, I would like to summarize a little what was said above, so if I correctly understood the situation, the fridge was working fine for three weeks until it couldn't maintain low temperature, removing the panel have solved the issue which means something with the airflow.
Either the fan motor is not spinning as it should anymore or a misplaced sensor that's not getting the right temperature, that's what I can think about so far and could you please upload some images, it could help.