Adding photos to a list

I have created a list and want to shift photos into it but I keep getting this error message: Failed to Add Items to List; SQLITE_CONSTRAINT: UNIQUE constraint failed: list_items.list_id, I do not know what I am doing wrong - a complete newby at this.

The error message is a bit misleading, sorry!

Most likely, this happens when one or more of the items you’re trying to add are already part of the list; it is an error, because an item cannot be added to the same list multiple times, but it is an error that you should not really have to worry about. We’ve already decided to change the behaviour to ignoring duplicate items, and adding the rest in the upcoming release.