Small Daewoo microwave 800w (Torre TA23)

This microwave is a few years old. It's been very well looked after so in great condition.
It has developed an occasional fault. Once in a while it just refuses to start. This can happen rarely - every few weeks or even months. At the moment it is working well.
Hard to diagnose a fault when it's working well but this was in an Airbnb so had to get a new one.