How to extract multipart RAR files using the command line unrar.exe

Short Answer

No, you are doomed, redownload is your best option.

Long Answer

You can start fiddling around with a hex editor and try to fix bad values in the RAR file, if you know how to define bad and how RAR works. But that's for sure a very hard route to take.

use 7-zip to extract them directly (don't use a file joiner)
Unlike Winrar , 7-zip can handle those .001 type files.If one of the archive is corrupt it will surely mention the part ( " crc failed in part x " ) but this will occur only if the data is damaged during downloading .
If this is not the case you can only solve this with the help of a recovery record. Simplest way is ask the person who uploaded the files to give you each file's checksumthen compare each of your own file's checksum with it the file with a different checksum is corrupted.