All baked shadows on transluscent materials are extremely sharp, no matter how large the lightmap resolution for the object is. This only appears to happen when the translucency lighting mode in the material is set ot surface forward shading. I’ve tried playing around with the other material parameters but nothing seems to fix the problem.
Surface Forward Shading utilizes the Forward Renderer, and that has a number of restrictions in terms of features it supports. I’m not sure if soft shadowing is one of the restrictions, but if it is, try using Surface Translucency Volume. Or, if you’re up for it, try modifying some settings to get it working with Surface Forward.
I’m making a note of it for forward shading limitations.
I figured it out! Apparently soft shadows on forward shaded, translucent materials only work with STATIC lights, stationary lights are not supported. This was a real head-scratcher for me yesterday. thatnks for the tip 
