Physics collision doesn't work as expected

I modeled a simple square box. It has 16 box collision primitives assigned to it, arranged in 4x4 grid to fit the box perfectly. Here’s an image to explain it better

On the surface of this box, I have put another smaller box with only one box collision primitive. I have enabled Simulate Physics and Use CCD on this smaller box.

Now when I add impulse to the smaller box in forward direction, I expect the smaller box to slide on the surface of the larger box and drop down on the floor once it runs at the edge of the larger box, but instead the smaller box keeps colliding with the box collision primitives of the larger box as if hitting an invisible wall and ricochets off of it. What should I do to make sure the box slides on the surface as expected?

(Note: The actual meshes in my project are complex, but I have simplified them and converted them to boxes in here for reproducing this issue)