I see. However I'm pretty sure that, actually, this is exactly what I'm talking about. I can't explain it any better since I have no real idea of how stencil shadows work, but I think the shadow volume is often quite big and interferes with the camera volume even where you wouldn't think of it. Whatsoever, this is just what my experiences with stencils are able to tell me. Probably you should indeed ask Conitec since they're probably the only ones who can provide you with a reliable answer.

EDIT: Here's another possibility that just came to my mind... Since, in your demo, the stencil shadow disappears if the figure's feet are close to the bottom of the screen, I thought probably the culling process could also be involved here? That is, probably the shadow is being generated from an internal copy of your model that, for some reason, gets clipped earlier than its visible pendant - for "performance reasons" or whatever