Self-intersection often fails to find intersections

I have been playing around with the PathVector intersection code, and it is very easy to make curves with self intersections that do not report them.

Here is a gif of my own code running the PathVector::selfIntersect. See how the orange dot (intersection) disappears at times as the curve is modified.

This is the svg path for a curve that I was able to get to fail on the unit test (self-intersections-test.cpp):

"M 210 258 C 321 198 171 23 160 95 C 149 167 307 251 318 253 Q 329 255 210 258 z"

I have not done too much investigation as to the why yet.

I'm running linux x86-64 and have tested both master and the wip branch of @S-Rafael .

Could be related to: #33 (closed) ?