I have noticed this warning message recently. I am not sure what it is and how to fix it? I have openhabian 2.4 on a RPi 3.
2020-01-16 19:20:50.772 [WARN ] [me.core.internal.events.EventHandler] - Dispatching event to subscriber 'org.eclipse.smarthome.io.monitor.internal.EventLogger@11a8939' takes more than 5000ms.