can you reproduce this behavior on BPMN Editor | bpmn-js modeler Demo | demo.bpmn.io ?
If so, please share a screen recording of the behavior you are experiencing. It is hard to understand what is happening from text alone.
Actually this behaviour is not on the bpmn online editor, it is in my app, although I haven’t defined any behaviour on clicking ctrl + z. I have used bpmn-js/lib/Modeler, ‘bpmn-js-properties-panel’, bpmn-moddle/resources/bpmn/json/bpmn.json libraries in the project.
Video link: ctrl + z issue (2).mp4 - Google Drive