Hello Thomas, how are you?
I had already noticed this change in the new versions of V-Ray and this impairs the visualization of the diffuse map in Blend Material as well.
In some materials saved in SketchUp V-Ray does not find the textures for Diffuse and leaves them empty if the texture is only in SketchUp XML.
I create a folder where I save all the textures used in the project so that they are not saved only in the temporary Sketchup folder or in the .SKM material for the V-Ray to recognize.
Maybe we would need to request a solution for the new version of V-Ray Next for SketchUp. What do you think?
Best Regards