After upgrading the version from 6.3 to 6.5, buttons no longer displayed in the component dialog window.
And they have the "hidden" attribute in HTML.
It's a customer component.
What could be the reason?
Please share dialog.xml
Remove jcr:Title property and add jcr:title property to dialog node(cq/gui/components/authoring/dialog) and check once.
If you still see the issue, try removing the extraClientlibs. Could be your custom override adding it.