I have had my SM150 for some years now it is a 2001 model. Still looks great, but I do like to clean it up really good sometimes and I can never seam to get it looking really clean on the inside. Usually I spray it down with degreaser and pressure wash the inside. Do not know it that is a good idea or not but it has never seamed to affect the working of it.
On the door function I have never gotten the error message that the door is open. It appears to have a magnetic type of switch. Just curious as to why it has never worked. It does not seam to affect the cooking at all.