arista sometimes finishes transcoding before EOF without error

I put a DVD in my DVD reader. Arista launches. I elect to transcode from the DVD to webm. Arista finishes without flagging an error, but the file on disk is only some initial part of the film being transcoded.

If there is an error, arista should flag it.

mplayer can play the entire movie off the dvd, so the media and hardware seems ok.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: arista 0.9.7-4
ProcVersionSignature: Ubuntu 3.8.0-25.37-generic 3.8.13
Uname: Linux 3.8.0-25-generic i686
ApportVersion: 2.9.2-0ubuntu8.1
Architecture: i386
Date: Wed Jul 3 21:18:12 2013
EcryptfsInUse: Yes
InstallationDate: Installed on 2010-03-13 (1208 days ago)
InstallationMedia: Ubuntu-Netbook-Remix 9.10 "Karmic Koala" - Release i386 (20091028.4)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: arista
UpgradeStatus: Upgraded to raring on 2013-04-28 (66 days ago)