You have configured a Carousel module in a page, but you cannot delete a banner associated with a certain slide, despite it appearing as empty:
The banner you see in the example screenshot above is not actually a module that can be deleted, instead, it is part of the Carousel module. As explained in Adding Slideshows on Site Pages Using the Carousel Modules, this is an optional feature of the module and will not appear if no text is present.
Therefore, to resolve the issue, please delete all text from the banner, including any whitespaces that may be present. In our example, a whitespace was causing the issue reported:
After removing any content from the text field for the banner, no banner should appear visible on the published page: