We have an instance of Shopify assigning the exact same order number to two different orders that were placed by different customers 2 minutes apart.
Shopify support claim that this can occur infrequently and that there is no solution. They say that the unique identifier is actually the order ID found in the URL. The only suggestion offered by Shopify was to cancel one of the orders and create a new one which is impractical to monitor given our order volume.
This is now causing customer service issues with other apps such as our returns provider which requires the order number to be unique, ie testing shows one customer will be able to place a return while the other will be blocked.
Does anyone have any insights into this problem and how to prevent it occuring?