It sounds to me as if you might be getting light interference from some other light source in the room with you. I get these same sort of effects if I have a lamp on across the room or an unshuttered or uncurtained window during daylight hours. Try removing any other light sources that may be in front of the camera. I use a floor lamp but keep it well off to one side and slightly behind the line of sight of the camera. I also wear a silver wedding ring and notice that if I reach up to scratch my nose while playing withe the TrackIr, it will pick up on the reflection from the ring and the tracking will go haywire for a second.
Make sure of this before you start messing with things like your dead zones.