Defect in Beveled Bezier Object

Observe the following image of a pipe created by beveling a Bezier curve using a Bezier circle.

Note the apparent defect in the object; it appears inside the red colored circle I have drawn upon the image. If the object is converted into a mesh or a N.U.R.B.S. curve then the defect no longer appears. What causes it and what, if anything apart from the aforementioned solutions, can be done to eliminate it?

Show us the wire frame.

It happens when the BevObj radius is greater than the radius of curvature of the curve path, but this is not your case.


Below are two partial screen captures of Blender showing the beveled curve as a wire-framed object. The first image shows it from front-view and the second image from top-view.