Thanks for the input.
The door DOES unlock after it cools down, so I guess the lock is
working but the latch sensor is bad. Because of the error code
displaying I assume I am hearing an alarm and not just a loose
vibration.

I will check w/ a nearby appliance repair shop, but I cant afford to
spend a lot of $, so I hope I can replace the latch thing myself. I've
never worked on an appliance like this, so I also hope someone can
point me to some illustrated instructions.