in past year, sometimes, when boiling water, the steam seems to cause microwave to quit working, even when using the fan.It would be off a few hours. The last few days I use it in the morning and then as soon as I cook oatmeal, that causes a little steam to rise, it goes off again. So it is off most of the time. What is the cause and can it be fixed? It is not under any warranty any more.