Mesh sticking to edges when using subdivision surface Amateur with Blender here, using 2.8, having an issue with the Subdivision surface modifier. I have a very simple shape here and I'm trying to extrude while using the modifier, I have this one part of the mesh that sticks to the edges of the model.



I've tried everything I could think even, I've even deleted all the vertices in that area and rebuilt it from scratch and that darn thing just reappears. If I delete all the edges and then just fill in the new face, it'll just move to the next edge down. I definitely don't have any overlapping points.
Normals are inverted either on right or left of the model.

To solve it:


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An easy way to detect this is to use X ray: