We have a Plone folder with three items (Plone 6.1.3) with album view assigned.
The album view renders all items twice for unknown reasons.
Any idea?
Have your folder "leadimage-beahvior" enabled? I remember me that this could be happen if a folder has a leadimage.
Good catch and solved with a custom album_listing.pt where I check for duplicated object ids for folders and albums.
Can you open an issue in plone.app.contenttypes, if this was the reason?