I just got three of the 933L cameras and I am getting a lot of false alarms, too. I have the cameras set to send video and stills; the stills show no change, but one video image (usually or always frame
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has most of the image black. The black image triggers the motion detection, and the still images don't show any trace. I am going to just send videos next.
Another cause of false alarms is cycling between color and IR, which is interpreted as motion.
However, what concerns me more is false negatives. My wife came home early and then left again; I got a video showing her back out, but not arriving before that. The motion zones should have picked up her arrival first.