Motion not dectected in close range

I have 3. The other 2 are perfect. The one on front door picks up motion 10 feet and out. Does not pick up motion within a few feet. My front door/porch is more of an alcove. So, it picks up everything beyond the edge of the walls - something like this configuration: l\_l I brought it inside and it works fine close up. I'm thinking now it's not receiving whatever signal it should in that particular spot. I there something I can add to enhance that other than moving it?