Sensor reaction on trees with "ignore static" option turned.

With "ignore static" option turned on sensor reacts on trees like if they were moving, which causes false actuations when trees are on the way. Or is it a reaction on foliage movement? Any case, it is pretty annoying.
Screenshots: pay attention to the light bulb on the sensor in front part of the chassis. No reaction on the wall, bush or rock, but reaction took place in front of the trees.