DVD Shrink is not more developed, and there were some little unsolved bugs in it.
Try this procedure (often it works).
[li]Rip the original disc on a folder [for example Folder_1].[/li][li]Open the Folder_1 files with Shrink.[/li][li]Save the entire disc with no compression on a different folder [for example Folder_2]. If you can, remove any unnecessary contents like foreign languages or other things.[/li][li]Open the Folder_2 files with shrink.[/li][li]Try again to compress the disc.[/li][/ol]
I hope that this will solve
Alternatively, there is a problem in the ripping method, because the ripped files still contains some structure protection that shrink cannot manage.
How did you rip the original disc?
EDIT: ooops too slow in typing