autodesk forge – THREE.js raycaster intersectObject method returns no intersection when checking if point is inside mesh

I want to check whether a point is inside a mesh or not. To do so, I use a raycaster, set it to the point’s origin and if the ray intersects the mesh only once, it must be inside. Unfortunately, the intersectObject always returns no intersection, even in cases I know that the point is located inside the mesh.
The point’s origin is given in world coordinates and the mesh’s matrixWorld is up to date too. Also, I set the mesh.material.side to THREE.DoubleSide, so that the intersection from inside should be detected. The mesh is coming from the Autodesk Forge viewer interface.
Here is my code:

mesh.material.side = THREE.DoubleSide;
const raycaster = new THREE.Raycaster();
let vertex = new THREE.Vector3();
vertex.fromArray(positions, positionIndex);
vertex.applyMatrix4(matrixWorld);
const rayDirection = new THREE.Vector3(1, 1, 1).normalize();
raycaster.set(vertex, rayDirection);
const intersects = raycaster.intersectObject(mesh);
if (intersects.length % 2 === 1) {
   isPointInside = true;
}

Why does the raycaster not return any intersection? Is the matrixWorld of the mesh taken into account when computing the intersections?

Thanks for any kind of help!