Item in gallery will not drag on top of a locked item

I have created and added items to the gallery to use in my project:

Unfortunately, when I want to use them in my project, they will not drag onto an item that has been locked.

Other items from the gallery will drag over the locked item, but not these items that have been created and added to the gallery.

Items that have been added to the gallery that are single items (not composite items) will also drag onto the locked item

The items added to the gallery consist of two items, not grouped, eg a level and a button item:

Please fix.