I can confirm I am also experiencing this same ‘duplicate posts’ bug since upgrading to version 2014.0805 of this plugin and have had to modify the FWP settings to not auto post syndicated sites (sets posts as pending, which is slightly inconvenient, but not awful).
FWIW, I was previously using version 2013.0504 with WP 4.1 and all seemed to work fine, so somewhere along the way this duplicate post bug was introduced.
