I have just finished a full resto on a GTB Atlantis and as part of post resto testing I noticed, very frustratingly, that 1 in 5 balls were not at first attempt being shot to the shooting lane. Upon removal of the apron I noticed that in every 'mis-shoot' case the ball was not sitting neatly within the double ball cam and the elongated return hole permitted, on occasions, a ball to sit slightly outside the double ball cam. After checking relevant ball return,relay and score motor switches I reluctantly decided to institute a mechanical solution. A screw to reverse the negative impact of the elongated hole. Perhaps not pretty but problem solved. I have never experienced this problem with the single ball cam round hole version.