Abaqus embedded truss problem

Hello,

 I'm trying to model a hollow pipe that have inside a 3D truss element. I've embedded the truss upper part in that cube shown in the picture attached.

The problem is when I apply lateral force what happens is that the bar just don't follow the pipe in its motion. The last mesh element in the embedded part isn't attached anymore to the upper cube.

I think the problem comes from that the tube is hollow inside. And the DOF of the 3D truss element is kept axial and the deformation of the element is just allowed into its axial direction and no rotation occurs

 Can anyone help me please ?