Hi all, I had the same issue and error message, but I could solve in a different way.
First of all, I wrote my diagram with the Zeebe modeler (version 0.9.1.1341) and everything was OK.
I could deploy the diagram to the Camunda Cloud (Zeebe on the cloud beta program).
Then, I made some little adjustments to the diagram and because it presented some errors, I re-wrote it with the same symbols and properties, but it began to present the same error you mentioned before “SAXException”.
Then, I closed the diagram and opened it again from the Zeebe Modeler and it throw the following warning: “unknown attributes ‘bounds’ [warning]”.
I searched this attribute in the XML and I found to which element it belonged.
I deleted the element and recreated it.
Since then, everything went OK.
Hope it helps you.