Though there are numerous causalities for a sales order to show up as open on a report, such as item or price changes when converting a sales order to an invoice, it has been maddening to see sales orders with absolutely no difference with the inherited invoice showing up as open.  This behavior has been a ghost in the QB desktop machine for many, many years.

I am relieved to report this hack of emailing of the sales order "auto-magically" fixes the error for instances where there is no discernible difference between the sales order and it's connected invoice.