USA, Alcohol/Ethanol Excise Tax

I was trying to setup Excise tax that we have to collect on certain items.
It is not a percentage - it is a fixed amount per specific item. (Different items have different Excise tax amount).

I tried (for 1 of the excise tax)..
-create TAX GROUP ..and assign to the specific items
-create TAX JURISDICTION (named it USA) and create the corresponding entry in TAX DETAIL (as tax type: "excise" and specific $ amount)
-added the TAX JURISDICTION to an existing TAX AREA

Created a sales order and ticked "TAX LIABLE" and set the TAX AREA to the one above
Added line item, one of the items on the TAX GROUP above

TAX shows as expected (including the excise tax).

But when I click on RELEASE:
-tax area on the order is changed automatically to the ship-to zip code.
-the TAX JURISDICTION i added above to the TAX AREA, is deleted from the TAX AREA

Do we have some sort of customization I'm not aware of - that does this "automatic" hocus/pocus" with the TAX AREAS?

We do not have developer license.
Our provider is too expensive and we avoid asking questions or asking for customizations. They charge for everything.