If all user's files have not been backed up, please check the following:
1) Data selection: Please make sure that you haven't unintentionally excluded such folders, files or file types that you would like to back up.
2) User privileges: Does both user and SYSTEM user have rights to the files? If reading rights are missing, files cannot be backed up either.
3) File status: Make sure that files are not locked or open. Locked or open files cannot be backed up.
4) Errors in logs: Sometimes errors like these can appear in the log:
"System.IO.PathTooLongException: The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters."
Hence make sure that the paths and file names are not too long.