I had run Duplicator once and it worked perfectly. Then I installed the duplicate site I had created to another folder on my server, made some changes to the new version of the site that I installed and then I tried to duplicate it again to make a backup, but then it didn't work.
It kept giving me error messages, but I checked all the possible issues it was suggesting and when I ran the test it showed everything was OK with my server. Eventually I just gave up since it was not going anywhere and I could not figure out what the issue was.
But then yesterday I discovered from my web host that I was having server space issues. My server space usage had increased by over 10gig. Eventually I realized a folder was created with large backup files files. It seems Duplicator caused this problem. And I am not sure why the files it created were so big or why it had added them to my server. The size of the site I was copying was only a few megabytes, but the junk files it created on the server were gigs.
Anyway, no worries. I am using another wordpress plugin for backup now which doesn't have any problems, but just letting people know that this plugin could cause your server to fill up with massive amounts of junk files and perhaps cripple your server storage allocation limits if things don't work right with it.