Problems with links within emails

Are you running a wordpress site? Double check the htaccess, plugins, and site files for modifications that are redirecting visitors based on their device and/or web browser type. It happens sometimes with hacked sites that only specific types of users will be redirected because they match the malware on the evil site, or simply to help prevent the site admins from noticing. If you are Wordpress, they have a scanner that can help - Gravityscan - Free Website Security Scanner

That scanner will work for other types of web sites too. Also, I suspect this may be a problem for all of your visitors, not just those clicking through the mailchimp link. What does Google webmaster tools report for your site? Google Search Console

Those links should have the tools to help you start to figure out what the problem is.

 

The WordFence team has a site cleaning option, they may be able to help you identify and fix the problem - Wordfence Site Cleanings - Wordfence

Before paying for their service I'd verify the problem is within your site. Do you know anyone with an android who can test going to your site and see if they get redirected when not following the mailchimp link?

 

Do you mind sending me a private message with your web site address? Maybe it's a DNS problem and you have an extra bad record in there, maybe a web server behind a load balancer that's not configured for your site, that type of problem. I'll take a quick look and see if I can spot the problem.

 

Near the top right of the page there is a link for "Inbox" that should have a red alert on it with a message from me - https://www.emailquestions.com/conversations/