These issues tend to be either an issue with the browser version directly or an issue that our SSL vendors have to fix. In order to properly diagnose this with our engineers, then please provide us with the following from visitors that are seeing the error in their browser:
1. The output from https://aboutmybrowser.com/.
2. The output of https://yourdomain.com/cdn-cgi/trace from their browser (replace your domain.com with your actual site's domain name).
Please provide this information in a support ticket so we can file a bug with engineering.