It is very rare for a domestic to require topping up, entails fitting a service valve, etc,

Anyway, the cold not creeping up into the fridge section, I vaguely remembered a similar scenario....

For the cold to travel into the fridge compartment, it travels via a duct which has a flap mechanism....

Something was disrupting this flow.......either a door not closing properly.........I cant remember, Ill have to try speak with the tech who was on that job with me.

All I remember it was strange,

Sorry I wish I could have helped more