Hi,
O.K. Here's what I get from the same scene and settings rendered first in LW and then in FPrime, both using background GI. No matter what settings I use in the nodal setup for the shadow catcher I can't get a shadow in LW. I have tried adjusting the sun intensity, the shadow catcher, the camera and render globals in all sorts of ways but still no shadow. And you can also see the illumination is a bit blown out in the LW render, even worse when rendered with the sIBL defaute of Final Gather. FPrime does render the shadow though.
LW Render

FPrime Render

All thoughts appreciated...