it´s probably a bird or something that just triggers the motion detection and before it takes the picture the bird is gone.
or ok if if cloudy and the sun and shadows triggers it .. well .. that´s probably hard to get rid of. .. you can of course lower your sensitivity on the motion detection ... but then again you might miss something.
Probably cannot avoid them since it is visual detection.
On a partly cloudy day the sun poking between the clouds or fast moving clouds will certainly trigger the visual differential. Moving and adjusting zones and sensitivity only helps so much ... to the point it will miss what you want to record.
The only solution is Passive Infra Red ... but it has its own limitations.