First, Thank you very much to the individuals that were actually interested in helping find and isolate the problem. I very much apppreciated your suggestions!
The problem was an intermittent short between the power wire and one of the signal wires behind the wall. This cable cannot be replaced due to the location so I will either need to relocate the sensor or go to a wireless PIR. Im sure some of you cant wait for me to try to install a wireless unit! :^)