Thanks — that API vs desktop isolation is exactly what I needed. It matches what we were seeing in the update path: healthy Item orders (layout metadata intact) accept a same-`Order.UID` PUT; the desktop-converted orders that land as Service / Item 404 do not. We’ll use the CFID and both UID pairs on a clone when you DM them.
On invoice Number during API conversion
You can keep the order’s number by setting `Number` on the `POST /Sale/Invoice/Item` body (same value as the order). The convert guidance sample does that explicitly:
https://apisupport.myob.com/hc/en-us/articles/360001247376-Convert-a-Sales-Quote-Order-to-an-Invoice
If you omit `Number` (or leave it blank), the API assigns the next invoice number — which is what you saw (00030356 → 00030357). That is expected API behaviour and is separate from the desktop retain-on-status-change preference.
If you set `Number` to the order number, check for duplicates if that number already exists as an invoice in the file.
For the historical desktop-converted invoices, the UI remains the practical workaround until we have a fix/data remediation path. Appreciate the thorough repro.
