Character Slowly sliding off platform

Hi i have a cube with a box collider and a rigidbody with the following values: mass = 1.4 drag = 0.05 angular drag = 0.05 use gravity = true

The platform (which also has a box collider) values: mass = 1 drag = 0 angular drag = 0 is kinematic = true;

The platform has a script which moves it in the Update function using rigidbody.movePosition(). The cube moves forwards jumping from platform to platform simply by adding 1f to the position on the z-axis. The platforms move left and right with the cube jumping from one to the other. However when the cube lands on a platform it will slowly slide to the edge opposite the direction of travel (so if its moving right it will slide to the left side or if its moving left it will slide to the right edge). The strange thing is that it doesnt always fall off, sometimes it will actually slide back to where it landed and other times it will fall off.

I hope this is enough detail of the problem. I have spent many many hours trying to fix this.