When looking at your list of scheduled parties, you may notice some of them may be highlighted with a Duplicate notice.
This means you have at least one post scheduled to go out at the exact same time of another post in another party.
This is not an error, but rather a courtesy notice. Your posts may still go out as scheduled, but it's not advised as Facebook has been known to block people for posting "too fast." Posting more than one thing at the exact same time will more easily catch their attention.
The most common reason this happens is when people use the same template for multiple parties scheduled on the same day, in which case every post in the party would show as duplicated:
How to correct this:
This is where the Adjust Post Time feature really shines!
First, click on the name of one of your highlighted parties
There is an Adjust Post Time box at the top of each party. Select the time increment you want to adjust that party by, then click Save Changes. All the posts in that party will then be moved forward or backward by the time increment you had chosen.
Example: I have a party that has an 8am, 8:30am, and a 9am post. If I select +5 from the Adjust Post Time dropdown box and click Save Changes, those posts will now be scheduled for 8:05am, 8:35am, and 9:05am.
Adjusting each Duplicated party like this often clears up any Duplicate notices from your list of scheduled parties.
Please remember that if you have many parties scheduled and many posts in each party you may still have a few posts in your parties duplicated; those can be fixed by using the Quick Edit feature.
Additional Note:
If you still have the error on the party but you don't see it on any posts then be sure to check the scheduled comments as well.