Samsung RS21 real temperature vs display

Last December I fitted a full kit of repair parts to the fridge side of my Samsung RS21.

The temperature took a day or two to settle down but since then appeared to be fine.

Now, though, the fridge isn’t cooling properly. The display says 3 degrees but milk is going off; we tested the temperature inside and it’s 10 degrees. We’ve since dropped the outside to 1 degree and the inside dropped to 8 degrees accordingly.

The cold water dispenser has also stopped working. The fan kicks in when I hold the light switch.

Have I done something wrong, or is there another sensor somewhere that didn’t come as part of the repair kit?

Thanks in advance.