What software do you use for alarm detection?
Or if it's directly from the camera, you don't have a "detection" sensitivity setting?
Another important thing is the environment; what does your camera capture, are there "natural" elements in motion (tree, road, or other...)
You can in this case, if your software/camera allows it, exclude "zones" not to be taken into account
There are several reasons for this kind of thing, either on the side of the Hardware part (adjustment) or on the environmental side
AD