First time customer subscription fails

[JosephMaxwell]

Hello,

We are running into a strange issue. After creating an account and going to the Newsletter page in the customer area and checking the Newsletter checkbox, the following error is displayed (and shown in the logs).

2017-09-22T16:15:00+00:00 DEBUG (7): Invalid Resource for Api Call: 
lists/11111a1f1b/members/member_id_here : Required fields were not
provided: email_address / email_address : Schema describes string,
NULL found instead / merge_fields.WEBSITE : Data did not match any
of the schemas described in anyOf. / merge_fields.STOREID : Data did
not match any of the schemas described in anyOf. / merge_fields.STORECODE :
Data did not match any of the schemas described in anyOf.

Here are our mappings:

This is a pretty vanilla setup. It seems to be a race condition with something else in the system as it doesn't happen after (presumably) the customer is created in MailChimp? I am not seeing the source of this problem readily, so maybe you have a thought as to what is going wrong?

Thank you.

[drewm]

Can you show the code you're using?