Well to be honest i’m not sure who to contact and what to say… We are premium user of Mailchimp, send newsletter to thousands, and your plugin does works great on its own, but since recently it stops other plugins to work normally.
When your plugin is enabled other plugins syncing on site is not working. When we disable your plugin, syncing across out multisite network works. But only in that case. And error we receive is related to Mailchimp plugin, when we check error log on server.