The invariant that you're assuming is a reasonable one, but unfortunately there are some anomalies due to bugs (hopefully mostly historical; the newest instance I can find is from January 2018). If possible, our intention is to clean up production data and then add a constraint so that more instances can't arise in future.
The invariant that you're assuming is a reasonable one, but unfortunately there are some anomalies due to bugs (hopefully mostly historical; the newest instance I can find is from January 2018). If possible, our intention is to clean up production data and then add a constraint so that more instances can't arise in future.