Crackling power point is scary, advice needed.

Ngaire Kerry from Feilding

The power point when used in my sons bedroom has on occasion crackled, sparked and smoked which is a real concern for us. I have twice had an electrician come and check/fix it and he can’t find anything wrong ..... nor can he say what it might be? Other than perhaps ants. Initially the TV was plugged in there but we unplugged it thinking it must be a faulty TV. Then we plugged the wall heater into it and it still happened. Hence my reason for calling the electrician in twice now. However, as he can’t see anything wrong and the power point works fine for a few weeks, it’s nervewracking when it starts crackling and smoking. I need some advice on what it might be so I can tell the electrician as he said unless it happens when he’s there, he can’t fix it. ANY thoughts on what is causing the plug to spark and smoke would be very much appreciated, it’s dreadful thinking about the consequences.