I currently can not solve a ray-quad intersection with a quad that bends, because it is impossible to solve (because really a quad can't/shouldn't bend).
Sadly, often times, models with quadrilaterals have impossible surfaces: some quads "bend" rather than be a perfect plane/polygon. You could break the quads up into triangles, but there are two ways to do that. And even then, what do you do with the normals? Keep the quad normal onto the two resulting triangles or just recalculate the normals? What is the industry standard for this process?