Have you welded the border vertices ? If not, make sure your border vertices are identically skinned. It's possible that there is a few units difference, and this is enough to create a physical break in the model.
@JohnnyRaptor vertices are welded. @EarthQuake I did what you have said and here are the result A. Baked the normal map without splitting the model. This does reduced the appreance of seam around the arm, But its still there. Although if you are not that close to the model seam wont be noticable. So this much apperance of…