You can set your Pan Scan limits by setting 4 custom waypoints. The first on the left and the 4th on the right will set your horizontal limits left and right while the vertical limits are set in each of the 4 waypoints.
However, that only applies to Pan Scan, not to Track Motion. There is no way to limit the Track Motion range of movement (which has been requested in the wishlist). If the cam gets distracted by perceived motion with Track Motion on, it could end up anywhere.
It sounds to me like you have Track Motion also enabled. It shouldn’t vary from the path between waypoints unless it is tracking motion. It will see it’s own IR reflection moving on the house and interpret that as motion. So yes, with the Track Motion on it will chase its own IR reflection on the eave or siding. With Track Motion off, it shouldn’t do that.