https://github.com/pantheon-systems/wp-redis/blob/4e8c04e1db484bd2f72a6b3d92532f7dd3ae40c3/object-cache.php#L1268C3-L1268C44

It appears that the "file_exists" function does not know how to handle files with tls:// prefix. the specific warning is

Warning: file_exists(): Unable to find the wrapper "tls" - did you forget to enable it when you configured PHP? in /pubwebdev/html/wp-content/plugins/wp-redis/object-cache.php on line 1259

That is a bit of a confusing warning, because in fact I have openssl enabled.

Perhaps an additional condition can be added here to check if the host is not tls.