Hello,
i already used this plugin in several websites without any kind of problem.
On my last (biggest) one i have backuping problems, here is the latest log.
here is the work in progress website http://www.studiovitruvio.it/v3 is not in the root folder, i will redirect the index once is finished.
Since the problem on the log file was zip archive one i tried this solution http://wordpress.org/support/topic/warning-a-zip-error-occurred-1
log of this problem http://pastebin.com/Vh5DiDqQ
but it didn't work so now i removed the line you suggested to add into wp-config.
On first instance i tried several backups but no one finished correctly, and the strange thing was the updraftplus disk space occupied (over 3gb)
So i wondered that updraftplus was trying to backup all the website folders and not the wp one. I deleted the biggest files on the ftp (some folders were used to deliver files to clients) and tried once more the backup, it still fails.
Please help :)
Kind regards