We discovered that Varnish cache that is used by some web hosts can interfere with Patreon unlock/login flows at your WordPress site due to its cache logic. Because the Patreon flow does not end by logging the user in at the traditional WordPress login routes and instead uses a specific url at your site that it has to use for being able to contact the Patreon API, Varnish cache can interfere with this flow by caching various aspects of your site.
If you are experiencing problems with your members not being able to unlock your content or login at your site, or if the members are not able to access content that their tiers should allow them to, do contact your web host and ask about varnish cache and whether it is caching your site at yoursite.com/patreon-authorization url. And if it does, ask them to configure the Varnish cache for your site so that it will not cache anything that happens at that url.