Cannot create invoice - "all these items have already been invoiced"

We are unable to create an invoice against a sales order.

Our sales order is for 8 700 items
We have then issues the following (I got this from the linked docs against the sales order):

  • INV-00274 1 080
  • INV-00269 1 296
  • INV-00252 864
  • INV-00244 2 178
  • CRN-00253 -2 178

I now have a delivery note for 216 items, but get the following message when trying to invoice against the delivery note.

I am unsure how to proceed. Any ideas why this is happening and how to get around this?