I am having an issue with the subdivision surface modifier in blender 2.8. I am getting this weird spike in my mesh when I smooth it with the modifier as if the vertex is unaffected by the modifier for some reason. There is no random geometry inside the mesh and there are no double vertices.
Solution: This was an issue with my normals and I found the solution after more experimenting. Blender 2.8 made it less obvious to see the directions of the normals. Also, CTRL-n no longer recalculates normals. The new hotkey is SHIFT-n for "recalculate outside" and SHIFT-CTRL-n for "recalculate inside". I hope this information will help a fellow blender user.