The structures relevant for credit management are S066 - open orders and S067 - open deliveries/billing.
You are looking at the wrong structure (S162).
Do you have authorization to run program CHECK_CM in SA38? This is the easiest way to check for most of the common problems in credit management. If you can run it, please post screenshots of the result for both orders.
Since you mentioned that the delivery block does not reset quantity confirmations for both orders, it seems to me that the most probable reason could be either different item categories - one relevant for credit update and the other - not, or not zero credit price for one if the items, or a rejected item.
So far I have assumed that you refer to the same order type and pricing procedure - please correct me if I am wrong. And also that you do not compare some really old order with a completely new one?
Is the issue reproduceable? Can you create exactly the same documents and get credit updates only for the first order? If not, then it might be a temporary problem with S066/S067 update. Your system administrator can check if there were some terminated updates at the time of order creation (if these are not very old documents).