If this happens at any time while the door is closed, please make sure that the laser is still pointed at the center of the reflective tag and there are no obstacles in its way such as safety release rope, spider webs etc.
If this happens when the door is closed but only during the (sunny) days, then it may be caused by the ambient light "blinding" the sensor. There are several solutions for this issue, reducing the threshold setting is being the simplest.
If false notifications happen only while the door is in motion, please check if the laser hits any highly reflective or closely located objects: metal panels on the door, safety release rope etc. Among the solutions: moving things around, covering reflective surfaces, increasing the threshold setting and/or scan period.