Lightmap shadow seems dirty?

Hello, I am currently exploring and learning things about lighting techniques. For now, I have a question that I can't seem to answer myself upon reading tons of threads about this.
I have here my sample scene, the shadows looks great when it is baked on the plane. But, the texture of my chairs does not have the "solid" looking shadow and it looks like dirt scattered throughout the chairs. It seems like the baking left some parts on the lightmap applied (low resolution? not enough texels?).

Anyone knows how to fix this? I tried using different models, and it still end up like this too.

Thank you so much.

 

in lightmap parameters (create your own if you havnt already) try setting pushoff to 0.001 or 0.01

 

Can you please help me was well, I will do whatever it takes to get my issue resolved. Skype Screen Share, make a video. I have over 500 hours in my prototype and I cannot get it to lightmap properly.

https://forum.unity.com/threads/lightmap-artifacts-everywhere-please-help-see-images.520639/

 

1. try to generate Lightmap UV using unity's model importer (select model in project tab and tick the Generate Lightmap UV from Inspector)
2. Select your target model in the scene and activate Double Sided Global Illumination option in the Material settings

Needs Unity 5.6.2+