Check this bracket to make sure it isn't bent. I had a MacBook that would intake or eject discs with difficulty; there seemed to be some obstruction in the disc drive opening. I took it apart and determined that the case opening (CD slot) was slightly out of alignment with the opening in the disc drive. I couldn't see why until I noticed that the front end (near the case opening) of this bracket was bent, so it didn't properly slide into the "slot" in the case chassis where it's supposed to go, thus forcing the disc drive to sit an mm or so high at that point, so it wasn't aligned with the disc insert slot in the case. I removed the bracket, straightened it, reinstalled it, and now everything works fine.

It should be noted for reassembly that this bracket should be slid toward the back end of the drive when it is inserted, then slid forward toward the front end so its "tab" goes into the "slot" in the chassis; then the bracket will be in the correct position to insert the screw. If the drive is put into its place with this bracket slid toward the front (opening) of the drive, there is danger the bracket may be bent, causing the problem I experienced. (I don't know when it happened in this unit, maybe when it was first assembled in the factory.)

I didn't look closely at these screws when I took it apart, but when I went to put it back together (two weeks later) I found I had two longer (4mm?) screws, and one short one. So I put the longer ones in the two end spots, the short one in the middle; they all seemed to go in okay. (Maybe the screws got changed around the last time the cracked top case was replaced, when the MB was in the Apple shop under warranty last year.)

The top two screws didn't seem to want to come out, and I saw no reason they had to, so I left them there, put a little piece of tape over each so they wouldn't fall out.