Sales Tax for Shipping Address not working properly

According to the infusionsoft forum, sales tax first looks at the shipping address, then the address on the credit card, then the billing address.

I run a monthly subscription and this has worked for me in the past up until this month. On some contacts, it used the billing address to pull sales tax, which causes a huge problem for me to have to reconcile those for the IRS. But on other contacts it did what it was supposed to and looked at shipping address.

What the heck is going on? Is there someway I can guarantee that it will always look at the shipping address? Is this a glitch?