They were scanned so long ago I don't remember the individual covers - but I am positive that I cleaned the scanner bed first AND scanned with a heavy magazine on them, and the lid closed. Some were straight out of the cellophane, so the covers themselves should be dust free. Also, I created a mini template, and everything was cut, cleaned and put into the template rather than just, scanned and uploaded.
Not sure what else I can do other than hang up my post as cover guru, as I obviously don't have what it takes.

Edit: this isn't me getting all pissy, or questioning that you found defects or questioning the quality standard that I myself love about this site. This really is me exasperated at having thought I had done everything, and created a clean cover, but still falling short.