saving error

hello everyone,

I create BPMN diagrams with draw.io in Nextcloud. When I revise them, the yellow dot on the save symbol disappears, but when I leave the diagram and open it again, the old work status is displayed. All changes are gone. I do not get an error message.
Can someone please help?

Nextcloud version: 29.0.8 - 29.0.8.1
drawio version: 3.0.3