Thanks for the reply Marianne, I processed the picture in Siver FX PRO. Maybe I should not do that.
It's better not to use such filters when uploading to Stock. Using such filters can introduce noise.
And Technical Issues here is also to do with contrast. I think the photo could be considered to be too contrasty and therefore not enough detail in the shadow areas.
Have a read of this. It's a brief guide on image quality and technical issues: