Possible API email bug

Okay so this seems like a weird one, hoping somebody here can help.

So I’ve been working on an app to transition store data from our old provider to Shopify, and being that the shopify customer import wasn’t quite up to what we wanted, I’m uploading them myself through the REST Admin API. So far I haven’t had a lot of problems, but I’m stuck on what to do about this one.

I noticed while testing my customer upload that email_marketing_consent wasn’t getting set for some customers, and as I drilled down into what was going on, it seems like Shopify isn’t letting me upload email addresses that USED TO BE in the system. If I go in to manually add a customer I can put the email address in, but while it does create the user, it comes back “email not provided”.

This is only happening for a few email addresses in my test data-set, but I can’t figure out why it should be having a problem at all, given that there are no customers in my store at all.

Thoughts? Ideas? Not sure if there’s some left-over data hanging around in the DB, but the API is saying 0 customers, so I shouldn’t be getting customers bounced over emails.

Thanks!