I'm not certain the approval coordinator is the issue. I just know that it isn't necessary when only one approval is required. That particular activity is useful when you have multiple approvals, example user A, group B (first approvals), group C (all appprovers need to approve) and you need to decide what to do with the multiple approvals. Does the first approval win? What happens if there's a reject? Since the output of the user approval is only approval/rejected, there's no need for the coordinator.
If you cannot reproduce it, that makes further tracking extremely difficult.
