Haptic Device Shadows

[vTony]

Hi,

We have a program which involves using a haptic device to pick up a screw from a colored box and place it into a hole with the same color (see "no shadow" image). We've started seeing a strange bug where if the user moves the haptic pen across the plane of the back of the screw boxes (the plane in the z-direction), some of the holes become darker (see "shadow" image). This only happens when the pen is within about a centimeter of this plane. There is a lot of code involved, so we were hoping there might be a quick/obvious fix someone could see just from these images. If not, I could see if I can produce a minimal case where the bug occurs.

Thanks in advance!