Yeap .. I was making the second model of the sub .. and even though I even published it here ... I´m not entirely happy with it since ... it has non-mainfold geometry! a pain in the *ss to bevel ... so i decided to see what the hell was causing all the trouble.

Turns out I used Extrude Edge and Merge Vertices to actually fill holes i would carve out from the sub itself. There´s my problem.

So I´m working on a new "version" of the same model but with 2-manifold geometry.

Thanks for the feedback.