Panasonic NN-SD27HS works only for 2-3 sec. false overheating error?

Hi,

this is my first question here.

My Panasonic NN-SD27HS performs very annoing error for quite a while.

It works perfectly ok, but with no reason sometimes it stops working after 2-3 seconds. Magnetron and turntable are off, only overheating fan is on for next 2 min.

Seems like defective temp. sensor, but this malfunction appears/disappears with no explanation...

No error code is displyed...

sometimes it helps, if I reduce the power to 440W

Can it be a kind of loose contact around the temp. sensor, or a capricious door switch mayby?

really no idea where to start checking....