Quality issue rejection

Hey, I'm trying to understand the reasons of rejection of series of shots, but can't figure it out - the histogram looks fine, there's no obvious noise (artifacts in the bottom left corner?). The rejection was quick, as if it was done automatically. What could be wrong here? I'd appreciate any help, as I'd like to avoid this happening again.
(Quality of the image was reduced, only 80%here because of upload size limitations).
