Zanussi ZI 918/12 K fridge freezer cooling problem

Currently got 7.5 degrees in fridge and around -14 degrees in freezer. Dial set to 6.

FF is in a rented house, so I can’t continuously monitor it. It has been switched off for 2 weeks and back on for about 5 days now when I went to investigate fault. Couldn’t hear compressor running, so pulled FF forward out of integrated unit and as soon as I moved it, the compressor fired up and kept running for a while. Don’t know if it was just a coincidence.

Before the 2 week switch off, it suffered massive ice build up in the freezer – so much that you couldn’t even see the drawers. I assumed this was through misuse by leaving door open or something, but wonder if it is connected to the problem?

FF doesn’t appear to have any vents to allow the cold air from freezer into the fridge, so I’m assuming it comes through the back wall, as this feels cold and has condensation on it.

I’d appreciate any advice or guidance

Thanks