Just a shot in the dark, but I was having tracking problems with my shuttle the last time I flew it. I was looking it over tonight, putting together a parts list, and noticed one of the bladegrips was a little sloppy. I havent checked to see if the screws holding them are tight, but it stands to reason that over time, those parts could become worn and sloppy even if the mounting screw is tight, as they must be free to rotate.