Even season veterans such as Till cannot escape the millions of combinations of site installs that may create corner cases that break software. Something in the latest 1.3.6/1.3.7 updates to his plugin, or possibly changes to WordPress, or changes to the underlying operating systems or PHP have broken the Redis Object Cache plugin.
This will manifest itself as a non-responsive website , usually with a basic 500 (Internal Server Error) reply.
The quick fix is to disable REDIS by adding this line to your wp-config.php file:
define( 'WP_REDIS_DISABLED' , true );
This will force the object-cache.php file that the plugin has you move into the WordPress root directory to not run any of the code within.
Wait for a future Redis Object Cache plugin update before turning it back on.