There are a few of possibilities. One is the drive is starting to fail. The other has to do with the front bezel door alignment, if it's "off" even a little, it can prevent the door flap from being opened as the drive opens. To test this, pull off the bezel assembly (it can be pulled straight off the mounting points), and then test the opening and closing of the drive. It could also be the drive sticking on the way out, test that with the bezel removed as well.
Jim