Outdoor Stickup Cam missing motion or starting too late

I have a new outdoor stickup camera and am trying to get the settings correct. It is 9 feet off the ground and 9 feet away from the back porch and door. People must walk or drive up the driveway beside the house to get to the porch. In either dark or daylight, with sensitivity set to almost max, someone can walk all the way up the driveway (about 40 feet), even weaving so they aren't approaching in a straight line, and the camera doesn't detect motion until they step up on the first step of the porch 15 feet away (and it misses that sometimes). When I was testing it on top of a step ladder, I could sometimes walk all the way up to the camera and wave my hand in front of it and it still didn't detect motion. This morning, I backed down the driveway, right beside it, and then returned, also driving right past it, and it didn't pick up any motion either time, until I walked back to the porch and stepped up on the first step. On the setup screen, the middle segment covers the driveway and the right segment covers my drivewway and even my neighbor's driveway and much of his yard. I have the left segment currently turned off since it covers only the house wall, but have tried it either way. While I was gone, I received a motion alert from it, but it never recorded anything. It's possible that a car drove past 50 feet away but there's no way to tell. I have played with all the various settings and none of them seem to affect anything. I realize PIR devices have trouble with motion directly toward or away, but I had hoped for a bit better than this. Does it sound like I've missed something?