[@Drew]
Aside from a lengthy reply I made which may or may not show up, it looks as if HDS Pro introduced a mechanism in Version 5 which seems to use ‘long reads’ upon encountering bad sectors (sectors which will just return errors if normal reads are attempted) to access whatever may be in those dubious sectors and then write it back, causing the disk to revector the sector without leaving any clue for the user (or file system) that it may contain garbage. HDS might have made the danger of doing this more explicit, but at least provided a list of files which might thereby be corrupted (though doesn’t mention doing anything to alert the file system if it includes possibly corrupt file system metadata).