I've lived with this problem for quite a number of years, and spent alot of time on this site trying to get some answers. Seems this has been a very common problem for this model. Since I have discovered that the main display board is no longer available, and noticed that we occasionally get flashes of the display when opening/closing the door, i'm wondering if the door latch "receiving" parts could be bad. The door is pretty hard to open, and also doesn't sit square when closed.
I still use it everyday as a microwave, but if possible would really like to access all the other options. I spend alot of time guessing about the temp/time setting on oven, and have gotten pretty good at it!
Any advice/help will be greatly appreciated!