I have some game cameras I made myself and some of the problems i've had are having a leaf or branch to close to the camera and when the wind would blow it would set off the camera. I think sometimes a bird will set it off and you don't get anything in the pic. I once set mine on a road in a clearcut just shooting across the road at the brush on the other side. All 24 pics went off the first day without anything in them, I guess it was wind moving the leaves on the brush across the road enough to set off the camera.