Unfortunately, there were some significant changes between version 6 and version 8.3.1. Both the header file style and the actual proprietary file system that we convert backed up data into have changed over the period of time between the release of those two version.
You would need to use version 6.3 or possibly 7.1. These versions are unfortunately no longer available for download. Do you still an installation of either version on any of your systems or the install packages by chance?
Technical Support Manager