If this is in-game, normally you get these hard shadows in case you have not re-rendered your light probes after adding a new atmosphere. Try removing that extra light probe, and instead select "Render all lightprobes" in the "Level" menu.
Ah ok. That makes sense.
I probably would have been unable to do as you suggest anyway though, since it's dynamic atmospheres for my day/night cycle (since the atmospheres are changed in code during gameplay), but thanks for the info. That's good to know for future projects
