After many backups, low budget horror movie --> audio sync problem in LiteOn LVD2001

[ohhowhappy]

I fixed the problem but, trying to not be so ignorant, I'm curious as to why it happened in the first place.

After making many DVD backups with DVDShrink and, lately, DVDRebuilder I had trouble making a backup of Carnival of Souls, a surprisingly good, very low budget horror film from the Criterion collection. Though either method would produce a DVD that played fine on my PC, audio was at least half a second out of sync on the LiteOn.

I was able to fix the problem by updating the LiteOn's firmware from 221 to 229. What I'd like to know is why this particular movie was giving me a problem. I've backed up copies of other Criterion films w/o difficulty, so I'm assuming that, although this film was cheaply made originally, that wouldn't make a difference after the transfer to DVD was made. But I can't think of any other variable. Thanks.