“Force re-check” option permits you to check torrents integrity. It means that the torrent content will be checked for missing files and pieces. Any incomplete file or piece in the torrent content will be removed during the re-checking process, and missing ones will start to download as soon as re-check is done. During the re-checking process downloading, uploading and seeding will stop. As soon as re-check is done, downloading, uploading and seeding will resume.
Usually, forced re-check is performed automatically by Folx when it is needed (for example, when you relocate your downloads; or when the download task was stopped and then restarted). But if you want, you may enable “Force re-check” option of torrents manually.
“Force re-check” option is available either from Main menu –> Tasks –> Force Re-Check, or from Status window –> Tasks –> Force Re-Check.