lftp script works in the console, but not via cron

Sample
------

#!/bin/bash
export
PATH="/sbin:/usr/sbin:/usr/local/sbin:/usr/local/bin:/usr/bin:/bin:/usr/games"
HOSTNAME="`/bin/hostname`"


# lft Variablen
HOST='1.2.3.4'
USER='user'
PASS='pass'
TARGETFOLDER='/'
SOURCEFOLDER='/backup'

/usr/bin/lftp -e "mirror --reverse --delete --verbose --log='/var/log/lftp.log'
${SOURCEFOLDER} ${TARGETFOLDER}; exit" -u $USER,$PASS $HOST


works fine in console, not via cron

my solution, install Version 4.7.1 from network repo instead of 4.6.4 from
default repo