I have the Whirlpool version of this microwave. Like many have reported here it began running as soon as I opened the door.
It worked normally otherwise. I tried cancelling the cook session before it ended as many have done with a cup of water but that did not fix it.
What fixed the problem for me was unplugging the microwave and opening the door, then plugging the microwave back in with the door open.
Let's hope this doesn't happen a bunch since mine is built-in and unplugging it is not a simple procedure.