Sales Order Cost not captured while onhand balance and item ledger cardex are not updated

Hi, I've been facing issues of intermittent problems with my sales order for a particular item. No Cost and cardex entries seem to be captured after finishing the Sales order cycle while there is a cost entered in the item master and item branch, where the item is using the item and item branch cost level. Can someone assist me on where I should look at in order to solve this issue? I've look through the item master, item branch and also the cost file. and all of these seems to be ok.. Help would be greatly appreciated. thanks