Fatal Error after upgrading to 2.1.8+

I’ve recently taken over management of updates for a WordPress site using W3 Total Cache. It originally was running 2.1.6. I seem to be able to successfully overwrite it with a fresh copy of 2.1.6 or 2.1.7 (downloaded from WordPress site). If I attempt to update to 2.1.8 or later, I get the generic WordPress Critical Error message in the main content area of any pages that involve this plugin (pages within the plugins’ management, the “Plugins” page, the “Updates” page, etc). I’ve reviewed various other threads and none of them seem to be matching the errors I’m getting.

After enabling WP_DEBUG, I get the following:
Warning: chmod(): Operation not permitted in /opt/bitnami/wordpress/wp-admin/includes/class-wp-filesystem-direct.php on line 173

Warning: chmod(): Operation not permitted in /opt/bitnami/wordpress/wp-admin/includes/class-wp-filesystem-direct.php on line 173

Warning: chmod(): Operation not permitted in /opt/bitnami/wordpress/wp-admin/includes/class-wp-filesystem-direct.php on line 173

Warning: chmod(): Operation not permitted in /opt/bitnami/wordpress/wp-admin/includes/class-wp-filesystem-direct.php on line 173

Warning: chmod(): Operation not permitted in /opt/bitnami/wordpress/wp-admin/includes/class-wp-filesystem-direct.php on line 173

Warning: chmod(): Operation not permitted in /opt/bitnami/wordpress/wp-admin/includes/class-wp-filesystem-direct.php on line 173

Fatal error: Uncaught Exception: Can’t write to file /opt/bitnami/wordpress/wp-content/w3tc-config/master.php in /bitnami/wordpress/wp-content/plugins/w3-total-cache/Util_File.php:375
Stack trace:
#0 /bitnami/wordpress/wp-content/plugins/w3-total-cache/ConfigUtil.php(74): W3TC\Util_File::file_put_contents_atomic()
#1 /bitnami/wordpress/wp-content/plugins/w3-total-cache/ConfigCompiler.php(199): W3TC\ConfigUtil::save_item()
#2 /bitnami/wordpress/wp-content/plugins/w3-total-cache/Config.php(379): W3TC\ConfigCompiler->save()
#3 /bitnami/wordpress/wp-content/plugins/w3-total-cache/Generic_Environment.php(31): W3TC\Config->save()
#4 /bitnami/wordpress/wp-content/plugins/w3-total-cache/Root_Environment.php(28): W3TC\Generic_Environment->fix_on_wpadmin_request()
#5 /bitnami/wordpress/wp-content/plugins/w3-total-cache/Generic_Plugin_Admin.php(742): W3TC\Root_Environment->fix_in_wpadmin()
#6 /opt/bitnami/wordpress/wp-includes/class-wp-hook.php(303): W3TC\Generic_Plugin_Admin->admin_notices()
#7 /opt/bitnami/wordpre in /bitnami/wordpress/wp-content/plugins/w3-total-cache/Util_File.php on line 375

As I’ve seen it referenced in several other threads, this deployment is explicitly setting ‘FS_METHOD’ to ‘direct’. The temp directory is set to a custom path that’s permissions are 777. The specified file (‘master.php’) is owned by the correct user and group for a Bitnami WordPress deployment, and is also permissions 777.