Does the fan stop going round too when the lights go off….but the element remains on ? I have had this particular fault and although i don’t think it was on this model it was on one similar. In fact i had 2 in the same week….and not had one since.
Anyway , it turned out to be the control unit. I suspect that contacts were making and breaking in there as it heated up but slamming the door was enough to close the contacts concerned…..quite an expensive repair if i remember too 🙁