I'm not familiar with your particular model, but virtually every microwave I've ever seen has as many as three door switches. One of them is to disable power to the heating section when the door is open, and another allows power to the turntable and fan when the door is closed.
It sounds like the switch that tells the microwave the door is closed has stuck closed, so the oven thinks the door is always closed whether it's open or not. The fact that one or two of the other switches is or are working is probably confusing the electronics as it's in a state that's not supposed to be possible with one switch saying the door is open and another saying it's closed.
Here's basically what it looks like; one of the contacts may be in a different position or it may have three contacts instead of two, but most of them are of this type.
[image|2791394]
You'll need to open up the cover of the microwave (ensuring it's unplugged, of course, and being careful of the electronics inside, as there are capacitors that can retain a large charge for hours after being disconnected) and check the door interlock switches for continuity and proper operation when the door opens and closes.