Printing sets Completed Sales Order back to Ready to Invoice because Back Orders and Sales Orders that were showing in drop shipment have a 'Print Pick Note' status even if it those are Completed.
The problem is due to a post-action that sets the Sales Order workflow to Read To Invoice regardless of stage. The fix is just to set the workflow to Ready to Invoice for Print Pick Note orders only.
1. Backup your database
2. Run the script "ReadyToInvoiceFix.sql" on the affected database
3. Run the application and check.
All Connected Business Versions