We have an old client site running EE2 (2.9.2) with Zoo Visitor (1.3.34) and @monooso's Mailchimp Subscribe (1.2) to automate signing up to mailing lists on registration.
Not quite sure why but lately the Mailchimp extension has broken user registration and updating user accounts. I know it is an old plugin (and since deprecated) but has anybody experienced similar as this is thought to be pretty core functionality by the client and is no longer working.
Delving under the bonnet it seems to be a lot of errors to do with how the extension is handling a settings object but finding it hard to debug. Disabling the extension fixes the user registration and profile updates but obviously, we lose the automation of Mailchimp subscription.