How to detect: In the 3D View the Bent Tube has a large loop that comes off the real-world tube.
How to solve: This is an extreme version of the wobbly tube above. Here there is some inability to solve a section of the tube well and so there is a gap and an offset in the underlying centerline data. When a curve is fit to this data, a loop results. If it cannot be fixed with better marking and better references on good photos, then this can sometimes be improved by changing the smoothing in the Bent Tube’s Properties.