Randomly not capturing

[RyGy7]

I have a random issue and am interested in anyone's thoughts or idea's. The fact that I can't exactly duplicate it has made it difficult to narrow down. I have a Foscam FI8910E on my front porch looking at the door. If a person comes up to the door it definitely captures, but if that person walks up to the porch then walks away zone doesn't seem to trigger. The alarm area is the entire screen and I have not found any errors during that time frame. Could the post be an issue?

[RyGy7]

Edit to this story i forgot the attached picture. Either way I discovered it works perfectly fine with humans, but I checked and it was deer tracks across the front. So zone makes deer stealthy..lol