Missing cashier python api example shows alert from beginning to end of video

Hi, I am trying the python api example with the missing cashier video. I am able to run the code successfully but the alert starts from around 1 sec of the video to the end. I opened the client and i can see zone is set and person is detected inside the zone. but somehow it still shows alert of missing cashier. I am using Detector Person Overhead Openvino and also tried other capsules but seems not helping.

any comments are welcome.

many thanks.

Please expand the alert region to cover the detect block.