Within FusionReactor errors will be tracked when an exception is fired during a transaction or the response code is in the 5xx state. You can define what errors or status codes will be in the error settings. For any exceptions fired the stack trace will be captured in the transaction details. If you have the Ultimate or Developer editions of FusionReactor you will also have access to the event snapshots. Let me see if I can grab someone from support who can help you here