How to reproduce:

Take a FileChooser with ACTION_SAVE.  Manually enter something as current name (into the top entry labeled "Name:"), or leave the application-supplied name if there is any.  Then select any folder that contains at least one regular file and no other subfolders.  Open the "Browse for other folders" expander if you haven't done so already.  Double-click any folder bookmark or the Home or Desktop place item.

Note how for a short moment, the first filename of the previously selected folder appears in the top entry (the current name) and how the entry is cleared afterwards.

This is really annoying when a default current name is provided by the application, like when downloading files with Epiphany.

I skimmed a bit through the code and found this in gtkfilechooserdefault.c, in the function shortcuts_activate_get_info_cb:

  if (!error && gtk_file_info_get_is_folder (info))
    {
      change_folder_and_display_error (data->impl, data->path, FALSE);
      focus_browse_tree_view_if_possible (data->impl);
    }

Removing the call to focus_browse_tree_view_if_possible seems to fix it.