Occasionally a ball image is partially on-the-rail, in addition to on-the-table. Why is this?

If this occurs on rails other than the rail nearest the projector, the system is out of calibration and must be re-calibrated. If this occurs only on the rail nearest the projector, this is normal and expected behavior of ICATS and is due to the angle of the projector and the rail raised above the table surface (~1-1/8"). This indicates you should place the corresponding ball directly against the rail. Alternatively, you can press v on the keyboard to vertically flip the layout, resulting in the ball(s) displaying against the far rail.