I’m still contending with the Dread Mailchimp Payment Glitch. In short, if your subscription is up for renewal but your credit card on file has expired or been cancelled, you will be repeatedly, automatically unsubscribed — even after you update the cc info. Mailchimp has been informed of this bug many times but shows no sign of addressing it.
If you get an unsubscribe notice, DO NOT TRY TO RESUBSCRIBE without contacting me first. I have to manually re-set your account to keep you from falling into the unsubscribe loop.
Apologies for the hassle.