Error - BPMN 2.0 Collaboration diagram export to BPMN format

Hello all,

I am using ARIS Architect and Designer 10 (education pack).

I have modeled BPMN 2.0 Collaboration diagram with some text annotation and I wanted to export it as a BPMN diagram.

But I am getting error. Please find attached file for more detail. I do not understand what the problem is.

If I try to export sub processes separately I am not getting error but if I tried to export main diagram I'm getting error.

Please guide me to solve this issue. I desperately need to export this model to BPMN format.

Looking for soon reply.