MC-3406: Explicit Background Attributes for Tab

 - ensure focused tab is set on load

Author: cspruiell

app/code/Magento/PageBuilder/view/adminhtml/web/js/content-type/tabs/preview.js

@@ -53,8 +53,11 @@ export default class Preview extends PreviewCollection {
                     // Ensure focus tab is restored after a rebuild cycle
                     if (focusedTab) {
                         this.setFocusedTab(focusedTab, true);
-                    } else if (activeTabIndex) {
-                        this.setActiveTab(activeTabIndex);
+                    } else {
+                        this.setFocusedTab(null);
+                        if (activeTabIndex) {
+                            this.setActiveTab(activeTabIndex);
+                        }
                     }
                 },
             });