Error 1000 occurs when converting several delivery notes into one invoice (= collective invoice, monthly invoices, collective delivery note).
This message indicates that the orders for these deliveries have incompatible header information.
If, for example, total discounts with different discounts are granted in the order, or terms of payment with different destinations, no total invoice can be formed from this.
An invoice has only one destination and only one total discount. In this case, you would have to convert the special cases into individual invoices beforehand.