I think you have rotated the XY-plane in your SOFiPLUS(-X) model, but the coordinate system within the SOFiSTiK Data Base (see Graphic) is still oriented in a different way. This has the effect that the cut line is located within the XZ-plane and is not working properly.
I have attached a short example for cut lines. It shows that a cut line (defined within the XY-plane) is working correctly, while the cut line located within another plane does not calculate suitable results.