Hmm. You mean that the shadow should be very blured, or just some blob or much less visible. Yeah that's either not possible at all or very difficult. Ugh, yeah shadows in SR were always buggy. To make it less visible we could adjust ambient (more) and diffuse (less), but heh, I fear that something could go wrong (not follow this, like water) IDK.
normally when you have clouds somewhere and the sun is behind these clouds, you don't have shadows (an option to disable shadows for a track could solve this)