Evaluate Length Bug

Hi all!

I have  a bit of a problem. The first step is to get the intersection curve of two intersecting pipes. The second step would be to fend the mid point on this curve by evaluating its length at  the 0.5 parameter. It should only result in one point but instead I get two. I have a list of these points and it only happens at one or two of them out of the many. Any ideas why this happens? 

All suggestions are welcome and appreciated. Thanks in advance!

Zoli

p.s.: I have attacheda picture of the problem.