Just check that the Torsion bar is straight and fit it into the tube without bushes.
With one spline engaged in the 'dogbone' in the torsion bar tube the end of the bar should be roughly central.
The last one we had with this problem would build OK with an OEM Bush from Porsche but not with an ER Polybronze.
This one was quite away out but the side of the chassis rail looked OK and it wasn't until we looked very closely at the tube where it joined on the other side of the rail we spotted the buckle.