Checkout Process Skips Step 1 - Shipping Information

When checking out, the shipping page is skipped and it brings me directly to the payments page, which is step 2 of the checkout process. I had a program developed restricting the combination of products from multiple categories and had to turn of the combined shopping cart option in the modules/pages/login/header_php.php file. The error only seems to be occurring 1 out of every 4 checkout attempts. Is there more to turning off the combining of shopping carts, if so how am I able to do so? If this is not the problem what would be the causing this error?

I am using version: zen-cart-v1.3.8a

Thanks

It sounds like the combine carts module you had written may be causing you some problems. Do you empty the customers_cart table each time the customer logs in, so as never to get an overlap? Are you being re-directed to the wrong page when you login? Do you have products setup which don't require the shipping address? This would cause the checkout to skip this page.

Absolute

Absolute:

It sounds like the combine carts module you had written may be causing you some problems. Do you empty the customers_cart table each time the customer logs in, so as never to get an overlap? Are you being re-directed to the wrong page when you login? Do you have products setup which don't require the shipping address? This would cause the checkout to skip this page.

Absolute

Thanks for you reply. After doing some testing, I believe the reason it was skipping was because some of the products where setup not requiring a shipping address. Thanks again for your reply it was very helpful.