After more phone calls and finally got the last stage of tech support from X'finity.
They sent someone to test the motion sensor and it was not functioning.
Instead of trying to trouble shoot and fix it, the guy just exchanged it with a new one.
Although the parts only had 30 days warranty ( not explained to me before ) X'finity decided to exchange this motion sensor at no charge. I simply told them I was unpleased, and why the 30 days warranty ? Did they expect the parts to go bad soon ? Never known anythng only offer 30 days warranty unless they expect the parts to break.
When asked what happened if I need to change battery later on because the sensors seemed to deactivate itself when the battery is taken out. The tech told me to call for tech support to change battery ! Okay, I had no clue that this system is designed to be baby sit all the time including to change the battery. Why ? Is X'finity worried DIY adding more sensors to the system ? Another thing, I was told if I add another sensor later on DIY style, they will charge me for the part even if I paid for it. This monopoly way of doing business is beyond understanding.
I am seriously considering dunking it after 2 years contract is up.