Recently I faced an very random issue about generating order without adding shipping cost. My client reported me that customer was able to complete the order without paying for shipping amount.
After reporting this issue, First of all I revised all of the error/debug log files [ system, exception, authorizedCIM, usps ] for further information about this issue but I didn't found any informative details from this files. Then after I checked the database entries of affected order and found that shipping method entry already available in quote table. But for some reason sales_quote data doesn't converted to sales_order data.
This means shipping rates was already assigned when customer was placing order but after place order shipping data doesn't inserted to order table. Please find below screen shot of affected order database entries for your ref.
Please help me to find out the issue or share solution if some one fixed this before.