I know I've seen this in more than one place, but I've just confirmed that it appears in the console on the item add/edit page: Uncaught TypeError: can't access property "backdrop", this._config is undefined _initializeBackDrop http://127.0.0.1:8081/intranet-tmpl/lib/bootstrap/bootstrap.bundle.min_24.1200003.js:6 On http://127.0.0.1:8081/intranet-tmpl/lib/bootstrap/bootstrap.bundle.min_24.1200003.js:6 <anonymous> http://127.0.0.1:8081/intranet-tmpl/prog/js/cookieconsent_24.1200003.js:20 <anonymous> http://127.0.0.1:8081/intranet-tmpl/prog/js/cookieconsent_24.1200003.js:197 bootstrap.bundle.min_24.1200003.js:6:52582 I think it's new since the Bootstrap 5 upgrade. Some web searches turn up information like "The problem is that the Modal has not been loaded into the DOM at this stage and therefore is undefined when the getElementById action is performed. The solution was to wait until the DOM is loaded." This would make sense considering the add/edit item page is one of those pages where the JS is loaded at the top of the page rather than the bottom.