@OldMan the issue is that your texture, even though is a seamless texture, it is not created with an equirectangular projection, taking into consideration some kind of deformation in the poles. There has been a lot written on how to map a texture on a sphere (think of a map of the planet earth)
all projections are going to yield some distortion, either when they are flat or when they are mapped around a sphere. The solution is having a pre-distorted texture (think mercator projection or an equirectangular environment sphere) that gets undistorted at the time of applying the texture on a sphere..
