Can't add some new sharepoint Bookmarks

We are trying to add some new SharePoint Online Bookmarks through admin centre but get the following errors when the csv file is uploaded

The item on line number ‎13‎ has a duplicate secondary trigger.
The item on line number ‎16‎ has a duplicate secondary trigger.
The item on line number ‎36‎ has a duplicate secondary trigger.

I've checked the rows against the list of all existing bookmarks and cannot see any duplication in url or title. Any ideas on what might be causing this / how to resolve?