We have an issue where the 'Usage per customer' setting on a discount is not being honored. That is, customers are able to re-use the discount code several times (Fig. 1) despite the 'Usage per customer' being set to a value of '1' (Fig. 2).
The only thing that stood out during troubleshooting is that the discount statistics do not appear to be updating based on the count of orders using the same discount code in the database (Fig. 3).