I also had a look at your model. As @AnnaFless mentioned your mesh is ok, the message in the Event log is only a warning that is related to a pre-step of the meshing.
The hexahedral meshing is not based on so called rich geometry formats as for example *.step or *.iges, but on triangulated geometries like e.g. *.stl. In general you should not care about this at all as the triangulation is done automatically prior to the meshing. In some cases, if the geometry model is not “clean”, the triangulation can not be done properly and there might be small cracks or duplicated triangles. The meshing is in general very robust in regards to those defects. That is why your mesh is still valid, but we expose this as a warning as it might help in cases where the mesh result does not look as expected.
I checked on your geometry model and it seems to be a clean sphere. Thanks @mlarreta for looking into the issue. I can also see those very small, irregular surfaces. It seems to be a visualization problem though. The geometry model should be fine. I reported both issues, the visualization problem and the irregular triangles, as of course for a valid sphere model the triangulation should not have any problems!
Thanks for reporting this! Helps a lot!