ahhh I see. something tells me that there is just enough movement in this that they are still reading open. the magnets is just a smidge too far away to register. maybe look into using a hinge instead of the tape so there is a defined track that the sensor will move on. I have used the hinge method as have many others and it seems to work far more than just the majority of the time. there is far less unanticipated movement with the hinge.