Critical VAT calculation issue

Hello,

I am experiencing a critical VAT calculation issue with your extension, which results in incorrect and legally invalid invoices.

On some orders, VAT is applied only to the shipping cost, while the main product is not taxed at all. This leads to wrong VAT amounts and incorrect totals on the generated invoices.

The issue is intermittent. Out of approximately 30 invoices, 3 contain VAT errors, while the others are calculated correctly. Unfortunately, I am unable to identify any clear pattern explaining why certain orders are affected and others are not. The configuration remains the same, and there are no obvious differences in product settings, shipping methods, or customer location.

The affected products are correctly configured as taxable, and shipping VAT appears to be applied properly. This makes the issue particularly difficult to reproduce and suggests a potential edge case or calculation inconsistency within the extension.

This problem has a serious accounting and legal impact, as it prevents the reliable generation of VAT-compliant invoices and makes the extension unsafe to use in a production environment.

You can find a screenshot of the incorrect order summary.

Could you please investigate this issue, confirm whether it is a known bug, and advise on a fix or temporary workaround? I can provide specific order examples, incorrect invoices, and my tax configuration if needed.

Thank you in advance for your support.

Best, jim