Apparently I have a broken CDROM drive.
This came to my attention when trying to make sense of the
CDROMCLOSETRY ioctl that behaved strangely. What happens is this: When I keep the tray opened and close it with the mentioned ioctl, the tray is in fact closed but I get an Input/Output error. If I try the same thing with my CD-Writer, the tray is closed and ioctl returns a value indicating success.
Note to myself: only use the CD-Writer when testing