if this is what i am thinking look into masking in the textures. Are these gaps small white slices? If so, look into masking the materials to stop the slicing where they come together.
Is it like this? I know this is from the older engine, but shows the effect i am talking about.
https://docs.unrealengine.com/udk/Three/TessellationDX11.html#UV%20Seams