The fridge is cooling too much or too little — why?

In both cases, the most likely culprit is a faulty thermostat that needs replacing.

Another possibility, if the fridge is not cooling properly, is that it may be low on refrigerant gas.

One thing worth noting: modern fridges use electronic thermostats, which can be quite problematic. A single power surge can be enough to cause a serious fault.

According to Archimede Lab data, temperature-related faults — not cooling, too much ice, not freezing, over-freezing — together account for 53.5% of fridge interventions.