What editor? There was a save editor for D:OS Classic, but it was not updated for the Enhanced Edition.
There is an
EE pak extractor (latest version
download), which should be able to read and extract the save.
After downloading, extracting and starting the program, switch to the 'PAK / LSV Tools' tab, in the 'Package path' browse to the 'Phantom Forest - 63h44m.lsv' file, then for the 'Extraction / source path' browse to that or another profile's savegames_patch folder and enter a new folder for the extracted files (you can copy/paste the path from the path listed above and edit it; ie to be '..\savegames_patch\extracted_save') and click the 'Extract Package' button. If that gives an error, very likely the save itself is corrupt.
An easier test (though not necessarily definitive) would be to right click the .lsv file and select 'Send To | Compressed (zipped) Folder'. Then check if the resulting file size is about the same as the lsv file, or significantly smaller. The lsv files are already compressed, so if they are much smaller when zipped, it likely means the files themselves are corrupt, and some or all of the data was zeroed out (so the game can not read the header information, so does not recognize them as saves).
It is certainly possible limited corruption could prevent the save from being recognized, but this will identify a lot of corruption issues.