In this commit: https://github.com/civicrm/civicrm-core/commit/
1602ec3e104de40e7bd785496f0cde323fe870ed the `display: none` was narrowed to only target divs with the class '.collapsed'. This excluded a few examples of fieldsets being used (as identified in ThemeTest, Accordion 4 - https://lab.civicrm.org/extensions/themetest/-/blob/main/ang/themetest/snippets/accordion4.html)
}
.crm-container div.collapsed .crm-accordion-body,
+.crm-container fieldset.collapsed .crm-accordion-body,
.crm-container .crm-collapsible.collapsed .collapsible-title + * {
display: none;
}