If the motion started outside of the mask (for example the wind moved the grass) it could still trigger detection of the objects nearby. You can observe the motion boxes in debug mode to check if that is the issue.
If you don’t want to detect the object in that area you can always set detection filter masks not only motion masks.
Or you can set the area of interest as a zone and only send notifications if an object enters the zone.
Frigate works by detecting motion and then running object detection on the motion area to check if any object of interest is there. So the motion detection is independent of the object.
The motion mask prevents motion detection from triggering in that area but If the motion starts outside the mask but it overlaps with the mask it can still detect object in the mask area.
Motion masks are not supposed to be used this way, it is highly discouraged. If you don’t want events from objects in the street then a required zone should be used
And yet I can’t understand why the setup is not working correctly. If I have specified that the pictures and recordings are only for cars, humans, cats, dogs and birds. And it captures any movement.