Issue with invoicing the customer twice, Using Scan Force to check and send data over to Shipping Data Entry

Why is it that I have had some customers get invoiced twice in a batch in shipping data entry?

Steps that I do: 

  • Scan sales order into Scan Force 
  • Scan items and send data to Shipping Data Entry
  • Wait a little bit for the data to send over
  • Scan order into shipping data entry and make sure that the lines under the shipped column match the numbers under the ordered column
  • Hit ALT+U which takes me to Starship
  • Enter in weight and dimensions
  • Hit F5 to print labels
  • Hit ALT+O for okay and then ALT+A for accept

When a customer gets invoiced twice, in the batch it shows the customer twice.

2 different invoice numbers same price but it only shows the sales order number on one of the invoices.