Why my mirror have seam ?

Peksio

Hello, I would like to ask You for Your help. I have a model, I properly did mirroring, I mean, I modeled low poly, deleted some of it, did uvs, copy lp, delete faces, merge, set soft edges and move uv shell by 1 uv unit. I did it couple of time with diffrent models and I never had any problems. But now I cannot get rid of this seam:

In substance it looks good but when I import this into ue4 this seam is very visible. Can You please give me some advice ?

Thanks and Cheers !

Obscura

try using full precision uvs. its a checkbox in the static mesh editor.