And basically the way to find that kind of problem in the solid is to use Edit > Separate to break it into individual surfaces and then turn on surface control points and examine them to see if there are any irregularities in the control point structures, mostly it's the tips and end areas that need some close examination to find those types of problems.

It also helps to jiggle the points around a bit if there is a suspicion that there may be some self intersecting areas, when you jiggle a point around you can then see if it was making a kind of zig-zag back tracking type pattern with its neighboring points or not.

The "Area" zoom tool also helps to get your view centered on a particular area at the end of a surface to examine as well.

- Michael