I created a new estimate and then use the "Process as..." contextual menu to create a new Invoice.
When I do this, the invoice draft shows up as locked and will not "unlock" when you click that button. It also shows the wrong items in the General window. The preview window shows the correct items.
Note - I have invoices sorted by "Nr" (invoice number, descending).
I believe when I Process the Estimate to a new invoice - the Draft invoice is showing the item details for the invoice that is sorted at the top of my invoice Documents list.
If I bring up the Documents list and select another invoice, then reselect the Draft invoice, it shows the correct items and is not locked/finalized.