Boolean modifier fails for certain configurations I have a set of outer meshes and inner meshes that are extruded cross sections along a path. The idea is to generate  OuterAsMesh - MiddleAsMesh. While it works most of the time, sometimes I get completely weird results from the boolean modifier. Attached is an example. There are three lines along which the outer and middle cross sections are extruded. The boolean modifier works completely fine for Line1 and Line2. However, when Line3 extrusions are introduced, the result just vanishes. In most other cases, only one arm will fail on the difference option unlike in this case in which the entire object disappeared. When the lines are moved around the boolean modifier can succeed but my actual object has many lines and moving lines around is painful and driving me crazy.
Can you please help me identify why the attached model fails. FYI, I have tried recalculating normals and that does not seem to be the reason.

Outer(Line1 + Line2 + Line3) - Middle (Line1 + Line2 + Line3) = Null!
Outer(Line1 + Line2) - Middle (Line1 + Line2)
This post Boolean difference modifier misbehaves with fluid sim has the answer. Adding a triangulate modifier solves the problem in the attached file.