Message "email - has already been taken" returned after customer_create success

[robertgivens]

Shopify is returning the error "email - has already been taken" when is successfully creates a new customer record with an email not in use for an existing customer account. The error is intermittent. Sometimes it returns the data customer record, but lately it returns an error more than it does customer record data.

I'm using the $_POST["customer_create"] method.