Default Credit Card set after submitting a sales order from the Store

A client has multiple credit cards on the customer record and there is NO default credit card selected. Once the customer places an order from the store, the last credit card used  becomes the default credit card. Even when the default is again de-selected manually on the customer record, the default credit card gets set again.

I'm not very familiar with e-commerce, is this a setting or is it likely that this is being set by a script? I looked at all the scripts related to the Sales Order and none of them seem to be setting this.

I have created a User Event that runs on afterSubmit on a Sales Order created from the web store to deselect the default credit card, it runs, but the default setting happens after my script and the default credit card still gets set.