Friendly tip to UX designers:
If other functions of your machine require the door sensor to be closed before they can proceed, please be sure the "Door Open" warning gets top priority if the display is only capable of showing one message.
Real world example: Customer in a panic because the machine says "toner empty" after they installed a brand new one.
One of 6 doors (unrelated to the toner and black plastic in a shaded area of the machine) is ajar by 1/4" due to one latch not fully engaging. The machine won't process the new toner because the door is open, but won't display the "door is open" message because the empty toner alert is already displayed and has priority.
#UXfail #OrderOfOperations