I have this strange problem - shadows appear below ground plane, it is like there is another groundplane just for shadows. How do I push them up at ground plane level? One note - 3d layer is created from file. Filetype: .3ds This is not just when editing 3d, but also when redering.
I've not see that before - it does indeed look like your two objects have come in with separate groundplanes.
Have you tried bringing them in on separate 3D layers then using merge 3D layers which should bring them into a single environment?
If you want to put the file up - I will take a closer look at it.