The same is true at my site:
Two motion sensors (z-wave, unrelated) trigger an event which switches a group of (two) zigbee lights on an off. Quite often, i see something like this in the log(s) when lights are switched off and not that often when switched on:
==> /var/log/openhab2/events.log <== 2020-05-18 22:12:04.212 [ome.event.ItemCommandEvent] - Item 'g_L_Sz_Bett' received command 0,0,0 2020-05-18 22:12:04.241 [ome.event.ItemCommandEvent] - Item 'Lam_Sz_BettLi_Farb' received command 0,0,0 2020-05-18 22:12:04.256 [ome.event.ItemCommandEvent] - Item 'Lam_Sz_BettRe_Farb' received command 0,0,0 ==> /var/log/openhab2/openhab.log <== 2020-05-18 22:12:04.914 [WARN ] [zsmartsystems.zigbee.ZigBeeExecutors] - Uncaught exception in thread TelegesisCommands-thread-16 java.lang.NullPointerException: null at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936) ~[?:1.8.0_252] at com.zsmartsystems.zigbee.dongle.telegesis.ZigBeeDongleTelegesis.telegesisEventReceivedRunnable(ZigBeeDongleTelegesis.java:776) ~[?:?] at com.zsmartsystems.zigbee.dongle.telegesis.ZigBeeDongleTelegesis$2.run(ZigBeeDongleTelegesis.java:752) ~[?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_252] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_252] at java.lang.Thread.run(Thread.java:748) [?:1.8.0_252] ==> /var/log/openhab2/events.log <== 2020-05-18 22:12:04.918 [vent.ItemStateChangedEvent] - Lam_Sz_BettLi_Farb changed from 39,100,35 to 39,100,0 2020-05-18 22:12:04.935 [GroupItemStateChangedEvent] - g_L_Sz_Bett changed from 0,0,0 to UNDEF through Lam_Sz_BettLi_Farb ==> /var/log/openhab2/openhab.log <== 2020-05-18 22:12:04.923 [WARN ] [zsmartsystems.zigbee.ZigBeeExecutors] - Uncaught exception in thread TelegesisCommands-thread-17 java.lang.NullPointerException: null at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936) ~[?:1.8.0_252] at com.zsmartsystems.zigbee.dongle.telegesis.ZigBeeDongleTelegesis.telegesisEventReceivedRunnable(ZigBeeDongleTelegesis.java:776) ~[?:?] at com.zsmartsystems.zigbee.dongle.telegesis.ZigBeeDongleTelegesis$2.run(ZigBeeDongleTelegesis.java:752) ~[?:?] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_252] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_252] at java.lang.Thread.run(Thread.java:748) [?:1.8.0_252]
It is not related to the system state (coming up or down that is).