It's probably the rubber band/o-ring in the drive (on the cogs) has become dirty, old-stretched. Replace it, I bought a $1 bag of Asst. rubberbands from the Dollar Store like two years ago, It's to the point where I need to buy another bag, the first one doesn't have any more small enough to double over and replace the bad band in the drive.
That is of course assuming you have your altered case lined up correctly. I have seen the Ghost cases, not put on perfectly "rub" up against the drive tray/bezel and prevent it from opening. But usually that's a none at all thing, and not a opens partially.