Order Total on Sales Order Totals Tab is Zero

We are running 2019 100c Advanced.  From time to time when entering a new SO the Order Total on the Totals tab is zero, while the total on the Lines tab is correct.  Oddly, the system allows the SO to be saved in this condition!  To correct the imbalance we close and reopen SO Entry, select and open the subject SO, hit the 'Item Price' button on the Lines tab, and the Order Total on the Totals tab is then correct.