I've been trying to reproduce it as well and haven't figured out the sequence. All I know is that it is happening far two often. I had two of them already this week. Being a U.S. company that sells into Canada, we require state or province. In the U.S., the incorrect injected shipping customer is always in the state of Alabama. We had our first Canadian issue this week as well and the injected shipping customer was based in Ottawa.
I'm unable to tell if it is showing the customer the wrong information ahead of them processing the order. I have confirmed that the wrong shipping information shows on their order documents and within the system after being processed. Also, the link of the incorrect shipping information doesn't ever link to the ordering customer's record. If we catch it ahead of shipping, I can switch the order's shipping information to the ordering customers correct address, and then that incorrect address that previously was linked is no longer linked to the order or the customer anywhere that I can see at the database level.