There were no errors at all in the console... I noticed that changing 'MSG Attack Blocked Both Players Disabled' as well as 'Enable Knockback' will not apply the effect with a /togglepvpreload, the server must restart to apply those changes, thus causing some confusions. Issue solved as I reconfigured everything... I don't know which part I have broken. Also I have a feature request: How about make these 'MSG Attack Blocked' messages less of a spam by adding a cooldown to them, or showing them in actionbar instead, or just an option to disable them?