We have a contribution page via an embedded short code that, upon submit, intermittently throws a "too many redirects" browser error. When this happens, the contribution is not written to Civi, nor does anything get to auth.net. Contributions do work successfully for some visitors, but not for others. For example, we can have success on a desktop, but then retest immediately on a cell phone and get the error message. Doesn't seem to matter whether the cell phone is on the same network as the desktop or if it's on it's mobile network. Also, doesn't seem to matter whether the user is logged in to admin or not. Clearing cookies or cache doesn't solve the issue.
We're running CiviCRM 4.7.15 on a WordPress (4.8.1) site. The site has a Let's Encrypt SSL and both the Wordpress general settings and the Civi base URL are the same (https). Server rewrite rules also rewrites to https. Caching is handled through CloudFlare and W3 Total Cache plugin. We're using authorize.net for our payment processor. All auth.net ip's are whitelisted in WordFence as well as CloudFlare.
Appreciate any suggestions or advice. We're stumped!