Toshiba DVD Recorder Service Mode / HDD Data Recovery?

I have a Toshiba RD-XS24 DVD/HDD, which has had its second once-yearly total data-loss from the HDD.

Actually, it's only the HDD directory sectors that have been corrupted, as when I tried to copy a title on the HDD there was a message in poor English that meant something like "the save process was not completed" - so I restarted the machine and received a message that the "disk was corrupted and that I could try reformatting the disk (which will erase all data)".

I then found that the whole Content Menu was blank - however, there was still only 0h29m left of free space - so obviously the data is still on the disk.

Are there any hidden service modes and/or HDD data recovery tools available to allow me to attempt to recover any of these recordings?

The Software version is YC13 / 12. It is still able to record directly onto DVD-R disks.

Thanks!