Wow that is a bunch! I would check inside your MailChimp settings. They can be set in such a way that no emails are sent or they can be set to require confirmations and welcome emails and so on. Those can quickly add up. Play around with the settings there and let me know how it goes.
I spent hours today researching it and trying to adjust every mailchimp setting I could think of, but it still did it. Spoke with the mailchimp support and they said it looks like a glitch in the widget. (See screenshot attached for full details.)
You’ve got me there. I haven’t heard of that happening to anyone else. United is the last theme that will have MailChimp built-in. There are so many widgets out there for MailChimp that having one in the theme just isn’t important anymore. But I would expect that if that’s happening in the other sites that run the same form, that I would have heard about it.
I’d just go with a plugin widget. This one is really just a sign up box so the integration with the theme is next to nothing. There’s no sense spending time on it. Just use a plugin.