I installed Duplicate Post on a development site this afternoon. I'm building a staff directory using four complex ACF field groups, making heavy use of ACF's Repeater add-on.
Upon duplicating one post, I've found that one ACF field conditional on the post editor page is broken - my conditional is not respected. After going into the ACF field group editor to double-check, I hit the Update button and all of the fields after the broken conditional are deleted from the field group.
I know this seems like an ACF issue, but I suspect it may have something to do with this plugin as well, since it only started occurring after I installed this.