How to connect "disconnected" edge loops between vertices It's just simple question, look at these pictures:





As you can see, I'm trying to using loop and slice, but edge is not connected. 

I tried to fix this, but it didn't worked(removing doubles, recalculate normals, remove faces that has not connected and re-fill it or etc).

What causes this, and how do I solve this problem?
Your mesh is non manifold at these spots. There are faces inside the volume which you have to delete.