How to have soft Shadow in build when using curved objects

Hello everyone
I’ve been having a problem when building the lighting of an apartment interior. how can we achieve soft shadows when a curved object is on the ground??
no matter what build quality or lightmap resolution i use, the shadow is always jagged. i tried with different Lightmass setting.
dose anyone know what i should do to fix it??

that’s a tough one bro! I hope someone can help you