PS i forgot some times when people sit down they twist this can move any fabric off grain in an almost permint way the wearer could be doing that so its shifted the threads in the fabric out of grain but usouly if the fabric is that loosely woven you can pull it back in to grain be grabbing it on the diagonal and stretching gently in the opisit direction of the slat this will help to reorient the threads back to 90 degrees