In some cases when a page is requested without a trailing slash (e.g. https://www.example.com/about) the cached file is returned instead of bypassing the cache to allow a redirect to a location with the trailing slash appended (e.g. https://www.example.com/about/).

Bypassing the cache to allow a redirect when a request to a page is missing the trailing slash, as WordPress currently does by default, was introduced to the Cache Enabler plugin in version 1.2.3 and added to in 1.3.1.

WordPress topic: https://wordpress.org/support/topic/do-not-cache-redirect-pages/