Liebherr fridge freezer behaving erratically

Great site, guys. Wonder it anybody can help me.

My father’s three-year-old £525 Liebherr upright fridge freezer has gone on the blink. The temperatures of both the fridge and freezer rise and fall erratically. The LED display behaves oddly (error code “F4” flashes). The Liebherr-recommended engineer came round and diagnosed the problem as a gas leak. He said fixing it would means replacing all the sealed parts, which wouldn’t be worth the cost. Basically, the fridge freezer is broken beyond repair. He advised him to go buy a Beko instead. My dad’s 80 years old.

My question is: can all this be true? Surely a gas leak would simply mean the unit would find it progressively harder to maintain the right temperature. Why would it make the unit behave in the manner described? Surely it’s one of the PCBs that’s broken?

I don’t want to waste money calling in another engineer (assuming I can find one willing to take a look) if there’s no point, but I don’t want to throw away a £500+ appliance if all that’s wrong is a PCB.

Anyone got any thoughts on this? Any help much appreciated