Can't delete symlinks on ftp sites

DOpus 8.2.2.4 (german) is not able to delete symlinks to non existent directories (error: "folder not empty").
That's neither a problem of the FTP-Server nor my rights on it, because other ftp-clients can delete the symlinks.

Do you get different results if you change the "Treat unknown links as..." setting on the Display tab of the FTP site?