fatal error after toggling Error Logging OFF

For DLM to work correctly, once you toggle error logging ON, you should see the following lines in your wp-config.php:

define( ‘WP_DEBUG’, true );
define( ‘SCRIPT_DEBUG’, true );
define( ‘WP_DEBUG_LOG’, ‘/path/to/your/debug/log/with_some_234087239834_random_sring.log’ );
define( ‘WP_DEBUG_DISPLAY’, false );
define( ‘DISALLOW_FILE_EDIT’, false );

When you toggle error loggin OFF, all five lines should be gone / deleted. So, that would explain the error you see:

Undefined constant “WP_DEBUG” in /home/mysite/wp-config.php:49

Could be another plugin that requires WP_DEBUG to be defined as true or false?

So, this is not specifically an issue with DLM.