After Effects :: Pre-composed Layers Not Consistently Casting Shadows

I've been trowling through th interwebs for an answer and it appears a lot of people have come accross similar issues yet I am still to solve my little hiccup.
 
I have a bunch of 3D layers sitting on a 3D plane. Everything was going swimmingly until I animated these layers in individual pre-compositions, when all the shadows disappeared. All shadow settings are set correctly, lights are in the right places, layers are separeted on Z axis and there are no effects on anything.
 
I'll include some images so you get the gist:For some reason, 1 shadow is working. i've checked all the settings and nothing seems to be different between them.

Here's a shot of the stats on the working comp:

And one of a non-working comp:

Now the pre-comps are no longer interacting with the ground at all. You can see the working one in the background is hanging out half way through the floor where as the front characters should be doing the same but aren't.

And finally, for some reason, at the 7second mark, it suddenly works again!?

Now, nothing changes at the 7 second mark, the camera and lights are in exactly he same place.