Technical issues unclear

I submit to a number of stock sites. All with high standards. Each has there own idiosyncrasies regarding reasons for rejection. In many cases they make no sense. What one site rejects another will grab. My guess is the phrase 'technical issues' is just an all-purpose term for knocking a few images back to give the reviewer a bit of authority. I have submitted images that have identical characteristics and there will always be few that are rejected for 'technical issues'. With Adobe it seems to  almost be a policy to reject a few, perhaps to make some vague point.