Some years ago we purchased a DMP502E1 electric oven and during the course of this time have experienced several problems necessitating calling service engineers to replace circuit boards and, I believe, on one occasion the thermostat.
Most recently, having switched the oven off after two hours use, we noticed that the fan continued to operate intermittently in short bursts of between three and five seconds. We assumed that although the oven was switched off, the thermostat was, in fact, cooling the oven down.
Some hours later, we were alerted to the smell of burning from our Kitchen and on inspection, found that although none of the lights on the oven’s facia were illuminated (indicating that the oven was off) the oven was in fact operating and, in view of the heat that was being generated and the charred remains of the earlier supper, it seemed that the oven was not being governed by the thermostat and reaching "cleaning" temp.
Despite our attempts to turn the oven off using the facia switches, the oven still continued to operate. Ultimately, we had to resort to switching the oven off at the mains.
Some two hours later, on re-connecting the oven, it still would not function correctly. The following morning, we turned the oven on at the mains and found that it could be operated using the facia buttons. However, when we turned the oven off after use, it still continued to operate.
This has now occurred on three separate occasions and, as you will appreciate we are most concerned that the oven has become unsafe and could prove to be a potential fire hazard.
I have contacted De-Dietrich on several occasions be e-mail and letter but to date have had no acknowledgement.

Ovens - De Dietrich - UMP404 Powerclean Stainless Steel Electric Single Oven