AP Invoice incorrectly calculating self-assessed tax

We are on 12.1.3, and in AP invoice workbench an invoice was matched to a PO and then the AP clerk clicked Calculate Tax.  They saw that the totals did not match, so they looked in Tax Details and found that there were 4 tax lines instead of 3.  One for city sales tax and one for county sales tax calculated at the correct rates, one for state sales tax with a rate of 0.00 (incorrect) and another for state tax with the correct rate but marked as self-assessed (incorrect).  The supplier is set up for sales tax, not for