Well a few years ago (2014) I submitted a track and they soft-reject it, at that time they had some time to explain why… and they simply told me the drums timing was not perfect… I did a very very slight adjustment and it was accepted.
Recently, I experienced a few rejections, and I always ask for some help here. Well, last time it was good advice: the track was a bit muffled, the mixing was not as good as it could be. I worked, and worked again, re submitted it and it was ok.
But… I still see some tracks that are accepted and I would personnally reject them: they sound midi, mixing is poor, and yet… they are validated! …