Doing a small test with spheres and capsules... I don't know if Physx is supposed to act like that..

First, here is the part of my code where I create the actors.

//1-Creating static plane	 
	PxTransform planePos =	PxTransform(PxVec3(0.0f),PxQuat(PxHalfPi, PxVec3(0.0f, 0.0f, 1.0f)));	//Position and orientation(transform) for plane actor  
	PxRigidStatic* plane =  gPhysicsSDK->createRigidStatic(planePos);								//Creating rigid static actor	
	plane->createShape(PxPlaneGeometry(), *material);												//Defining geometry for plane actor
	gScene->addActor(*plane);																		//Adding plane actor to PhysX scene

	int numberofblocks=50;
	PxVec3 offset = PxVec3(0,1,0);
	PxReal radius=1;
	PxReal height=1;

	//initialize a chain
	PxTransform		boxPos(PxVec3(0.0f, 1.0f, 0.0f),PxQuat(PxHalfPi, PxVec3(0.0f, 0.0f, 1.0f)));	//Position and orientation(transform) for box actor 
	PxRigidDynamic	*gBoxOri = NULL;				//Instance of box actor 
	PxCapsuleGeometry	sphereGeometry(radius,height);											//Defining geometry for box actor
					gBoxOri = PxCreateDynamic(*gPhysicsSDK, boxPos, sphereGeometry, *material, 1.0f);		//Creating rigid static actor
					gScene->addActor(*gBoxOri);														//Adding box actor to PhysX scene

	for (PxU32 i=1; i<numberofblocks; i++)
	{
		PxTransform		boxPos(PxVec3(0.0f, 2*i*2.0f, 0.0f));												//Position and orientation(transform) for box actor 
		PxRigidDynamic	*gBox = NULL;				//Instance of box actor 
		PxSphereGeometry	sphereGeometry(radius);											//Defining geometry for box actor
						gBox = PxCreateDynamic(*gPhysicsSDK, boxPos, sphereGeometry, *material, 1.0f);		//Creating rigid static actor
						gScene->addActor(*gBox);														//Adding box actor to PhysX scene

						// adding some joint to the mix
		//PxSphericalJoint* joint = PxSphericalJointCreate(*gPhysicsSDK, gBoxOri, PxTransform(-offset), gBox, PxTransform(offset));

		gBoxOri=gBox;
						cout<< i <<"\n";
	}

When I visualize the simulation in the PVD, I see the spheres falling down as expected. Piling up.

The funny thing is while they spread after bouncing, they appear to only move in the X,Z plane completely ignoring the Y dimension.

By replacing the spheres by cubes, the objects explore in X,Y and Z.

Can anyone tell me if PhysX is supposed to act like this with spheres?