DVD Tray doesnt eject in vertical position only

Hello All
I have been having a peculiar problem with my Sony DVD RW Drive 810A.
I have been having this drive for the past 2 years and it has worked fine so far.
I have installed it vertically since my machine sits vertical because of space constraints.
Now for the past few months when I press the eject button on the drive the drive tries to eject but I hear knocking noises and it doesnt come out. However I can eject by selecting that from the windows explorer though !!
Later on it came to a point thta even this wouldnt work.
The only way I can now eject this out is if I use the safety pin that comes along with and I poke it into the hole below the tray.

These are the observations :
1) The tray doesnt eject when in a vertical position.

2) If I have a DVD in the drive then it ejects when I press the eject button even in vertical position.

3) The tray works FINE in a horizontal position.The eject button works and the drive is all fine.


Any idea what this could be ? Seems it has to do with something that props in when the drive is only in a vertical position.The software and hardware components seems to be fine since it all works fine if the drive is operated horizontally..

Really puzzled.Pls help me.
Thanks folks

Alex