Periodically there is such a message
ScheduleAuctionTask: Failed scheduling auction 51
java.lang.NullPointerException: Cannot invoke "org.l2jmobius.gameserver.model.actor.instance.PlayerInstance.getInventory()" because the return value of "org.l2jmobius.gameserver.model.items.instance.ItemInstance.getActingPlayer()" is null
at org.l2jmobius.gameserver.model.items.instance.ItemInstance.setEnchantLevel(ItemInstance.java:937)
at org.l2jmobius.gameserver.model.itemauction.AuctionItem.createNewItemInstance(AuctionItem.java:84)
at org.l2jmobius.gameserver.model.itemauction.ItemAuction.<init>(ItemAuction.java:88)
at org.l2jmobius.gameserver.model.itemauction.ItemAuction.<init>(ItemAuction.java:72)
at org.l2jmobius.gameserver.model.itemauction.ItemAuctionInstance.createAuction(ItemAuctionInstance.java:531)
at org.l2jmobius.gameserver.model.itemauction.ItemAuctionInstance.checkAndSetCurrentAndNextAuction(ItemAuctionInstance.java:315)
at org.l2jmobius.gameserver.model.itemauction.ItemAuctionInstance$ScheduleAuctionTask.runImpl(ItemAuctionInstance.java:414)
at org.l2jmobius.gameserver.model.itemauction.ItemAuctionInstance$ScheduleAuctionTask.run(ItemAuctionInstance.java:394)
at org.l2jmobius.commons.concurrent.RunnableWrapper.run(RunnableWrapper.java:38)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
at java.base/java.lang.Thread.run(Thread.java:832)