Timing is important if you are always behind in posting output versus shipping. If you are attempting to ship 100 units but have only posted output for 10 then there isn't enough of actual inventory (reserved for the sales order) to ship against. It doesn't matter if this is on one or more production orders. If you have 2 production orders and posted 100 output for Prod. Order #2 and then tried to ship 100 for your Sales Line, I would imaging NAV wouldn't care and just ship that 100 that's available. I'm not 100% sure on this though since I've never worked with this scenario before.When you get an error if you go to the Sales Line in question and go to the Line menu, Related Information and select Reservation Entries, the page that opens should show you where your reservations are being Reserved From. Look for ones that are reserved against Item Ledger Entries and make sure there is enough quantity of those to match what you are shipping.
If you've found this thread useful, dive deeper into User Group community content by role