Fixture ID: allowanceRated_G · XPath: /ubl:Invoice/cac:AllowanceCharge[1]/cac:TaxCategory/cbc:Percent
The document level allowance at allowances[0] uses VAT category G (Export outside the EU), so its VAT rate (BT-96) must be 0 (zero), but it is 19. Goods leaving the customs territory of the EU are relieved of EU VAT; whatever tax the destination levies on import is assessed there, on the importer, and has nothing to do with this document.
BR-G-06Set allowances[0].vatRate to 0, or omit it — this library normalises the rate for category G either way. If you did mean to charge 19% VAT on this allowance, the category should be S instead, and that will change which breakdown group it nets into.
"vatCategory": "G", "vatRate": 0