While I see your question was partially answered in Getting incorrect iteration and http_req metrics when running parallel scenarios - #5 by kaushik, this is a feature that’s unfortunately not very well supported by k6 right now… 
You can generate a report like this with k6 OSS, but it would require either messing with external outputs or with log parsing and processing…
So I created a new issue to track this: Expose a list of errors (with their counts) to the `handleSummary()` · Issue #2158 · grafana/k6 · GitHub