DVDShrink is probably the least robust decrypter/ripping program. If I were attempting this, I’d use DVDDecrypter. You can set the read error retries to a higher number than the default 20.
If you know the dvd has an advanced protection that DVDDecrypter can’t handle on its own, you could run AnyDVD in the background to deal with that.
Its probably not worth the trouble though, with physical defects in the disk, you are not likely to rip it successfully. The odds are very much against it.
Writing to the manufacturers is just about the only step left I would think.