Multi Instance: How to find out which iteration failed?

I am implementing a BPMN process that is using a parallel multi instance activity. My question is when one or some of the iterations failed, how do I find out which one failed through cockpit, and what variable it is using?

Thanks in advance for your help!

In the image, **_list is the collection and **_ids is the element variable.

This is the model.

Would really appreciate any help!