Re: Extrude a hatch pattern?
My first guess is that the exploded line pattern is not closed. Even though it looks that way. And, more like than not, the lines extend "past" an intersection, rather than being open.
Two ways to test. Create a test layer, and see if you can solid fill (bhatch) the geometry you want to extrude. This will show you open versus closed.
Or, use Boundry (on a new layer) to cast extrudable plines from the exploded hatch 'shapes.' Boundry works just like BHatch, so it's fast--but be carefull, the boundries are 'linked' just like a Hatch (so they will Extrude in a group if formed in a group). Good for some things, not so for others.