When the camera is triggered by motion, Blue Iris sends Sentry AI the first frame of the motion clip. Under some special settings and camera positions, the motion is triggered first and the human only appears many frames later resulting in false negatives.
One way to fix the problem is to define an area of interest (zone). In the sample image below, Blue Iris is configured to create a motion alert only if there is activity in front of the door.
This technique is very useful at front doors. If the camera is not positioned perfectly, then often times the camera triggers when the front door is opened but the person only exits the door many frames later resulting in many false negatives.