Issue creating triangle mesh in PhysX - c++

Question

I've constructed a quick python script that reads a wavefront .obj file and outputs the verticies and faces to files. I have another C++ function that reads these files and creates a mesh based of-of those.
The issue that I'm experiencing is that this works perfectly sometimes, and other time not so much - with the same mesh. E.g. I start my PhysX program, and create 10 of the same objects of the same mesh and some of them look like this:
and others look like this:
The following C++ is the code that loads the verticies and triangles:
bool ModelLoader::LoadVertexFile(const std::string& fileLocation)
{
std::ifstream file(fileLocation);
if (!file) {
std::cerr << "Failed to load vertex data\n";
return false;
}
float x, y, z;
vertexArray.clear();
while (file >> x >> y >> z)
{
vertexArray.push_back(PhysicsEngine::PxVec3(x, y, z));
}
return true;
}
bool ModelLoader::LoadTrianglesFile(const std::string& fileLocation)
{
std::ifstream file(fileLocation);
if (!file) {
std::cerr << "Failed to load vertex data\n";
return false;
}
int x;
triangleArray.clear();
while (file >> x)
{
triangleArray.push_back(x);
}
return true;
}
This is the code for creating constructing the mesh
CustomObject(const PxTransform& pose = PxTransform(PxIdentity), string vertfile = "", string trigfile = "") :
StaticActor(pose)
{
modelLoader = new ModelLoader();
if(!modelLoader->LoadVertexFile(vertfile))
throw new Exception("Failed to load VertexFile.");
if(!modelLoader->LoadTrianglesFile(trigfile))
throw new Exception("Failed to load TrianglesFile.");
PxTriangleMeshDesc mesh_desc;
mesh_desc.points.count = (PxU32)modelLoader->vertexArray.size();
mesh_desc.points.stride = sizeof(PxVec3);
mesh_desc.points.data = &modelLoader->vertexArray.front();
mesh_desc.triangles.count = (PxU32)modelLoader->triangleArray.size();
mesh_desc.triangles.stride = 3 * sizeof(PxU32);
mesh_desc.triangles.data = &modelLoader->triangleArray.front();
CreateShape(PxTriangleMeshGeometry(CookMesh(mesh_desc)));
}
So if anyone can help me figure out whats going wrong it would be really appreciated