When a diagram is exported into XML some definitions are not in the right order compared to the bpmn schema.
As per BPMN schema (see below) the “dataOutput” is supposed to be defined before the “outputSet”. In the exported file this is not true.
Here are both files, the original and the one that the online bpmn.io editor exported when using “Download BPMN diagram” button. The problematic part can be seen in the StartEvent element with id=“ID_StartEvent”. diagram_original.bpmn (30.5 KB) diagram_exported.bpmn (29.9 KB)