Order sequence wrong after complete

[marcalwestf]

The document no of the order (=sequence) gets disrupted after the order is completed.

Here the steps to reproduce it:
1.- Create an Order. It gets the document no n
2.- Add a product, enter a quantity and pay. The order is then completed.
3a.- In Swing, create a new order (F2).
3b.- in Swing, a new order is automatically created. Add a product.

As a result, the document no of the new order is n+2 instead of n+1.