JL1, that is a know problem - dubbed the "Deranged Traffic Light Thang" aka "Disco Lights", there is a specific thread here for more info. Please post you experience on that thread as it will help to show WBS that this is a widespread problem.
Before the wbs web site went on the blink, Centurion was indicated as 'in planning'. Can't check at the moment. Are you certain that the tower at Erasmuskloof is operational? AFAIK only Wonderboom and Sunnypark are operating. You are probably picking up Sunnypark at a distance of 15km.