Tax Issues

So I have a customer do a order and it does not charge them tax on it. Then they place the second order for the other son and it charges tax on that order. The address is the same. 

This has happen 15 times over the last 153 orders.

Any help with this

And the orders not getting charged tax is the product marked as taxable? (edit the product to check the taxable option). 

Yes I can confirm they are ordering the same product. I have also confirmed that the product is check as taxable. I have setup 5 production only for this group of players. All the 5 productions are setup the same way with the taxable checked.

You will need to email me the following for me to look into it as I can not duplicate the issue and no one else experiences this issue: 

• 1) The link / URL to your Sytist admin (where you log into your Sytist admin).
• 2) The admin username and password (or create me an admin account by clicking Admins in the upper right corner of the admin pages).
• 3) The order numbers of 2 order in  which one was charged tax and the other not.
• 4) Link, username and password to your hosting control panel so I can access the database and files.