this is a known error. Just don't use immovable boxes to make a floor.
I descriped the cause last week but there is no real fix, because it's a bug by design :)
As you can see i drawed the collision points -> red dots, and the collision normal -> green lines. In theory there should be on of these line-dot combination (the right red dot) but the engine is based on impulses and does allow penetrations of objects by design (very small penetrations of cause)…. => So the sphere sinks in a little, and therefore we get the second collision point (the left red dot) because the sphere intersects with this box now. This is results in jumping of the sphere.
You should use a triangle mesh for your game to let the sphere roll. There we have the same problem when the sphere is on two vertices at the same time but I posted a workaround for it here: here