I got hold of a Apple CD 300 (SONY CDU-8003A) drive that turns on and shows up on the SCSI bus when I list all the devices. I when I try to put a caddy into it, it just ejects the caddy instantly. I opened it up and cleaned the laser head with some alcohol, but it still acts the same way. 

After I cleaned it and put it together the caddy slot won't open automatically any more either, so I have to manually open it for the caddy to be ejected. Everything looked ok when I opened the box, no faulty hinges or anything I could see.

Does anyone have a idea how to fix it?