two requests for the same code. Two orders from the same customer, but with the same code.

[nivaldo]

Good afternoon. I own the store www.topmagicas.com and I have a strange problem. I use PS 1.6.1.11

In my store, we offer free shipping to all categories, except one (BAZAR MÁGICO), everything seems to work fine but ...

1- If the customer purchases a product from
"BAZAR MÁGICO" category freight is normally calculated;

2- If the customer buys products from other categories, the freight is not charged, all right until then;

3- The problem occurs when the customer makes a purchase of a product of the category "BAZAR MÁGICO" (Freight Paid) and also of another product, in another category (with Free Shipping).
When this occurs, 02 orders are generated with different numbers but the same code, so far so good, it's strange, but come on ... The problem is that the freight value of the product with freight paid is not calculated nor added to the final value. This is bringing us a lot of upsets.

Can someone give a tip, please?