Well that is strange. Have you checked the status of the door on the garage page in Alarm.com? When this happens is the door reporting that it is open after it opens? Or does the app show the garage door as in the wrong state?
Also: How long have you had the MyQ installed? Has the controller been working properly for a while and only recently started doing this? Is it new and is predominantly malfunctioning? Has it been a long time and only happens once in a long while?
If it is the 821LM using a tilt sensor, I would check to make sure first that the orientation of the MyQ Tilt Sensor on the garage door is correct. “Top” is written on the side that should face up.
Do you have more than one door connected? If so does this happen to both or only one?