[09:51:52] [Server thread/WARN] [minecraft/NetworkSystem]: Failed to handle packet for /192.168.1.119:35183
java.util.ConcurrentModificationException: null
        at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445) ~[?:1.8.0_212]
        at java.util.HashMap$KeyIterator.next(HashMap.java:1469) ~[?:1.8.0_212]
        at net.minecraft.entity.EntityTracker.sendLeashedEntitiesInChunk(EntityTracker.java:386) ~[ol.class:?]
        at net.minecraft.server.management.PlayerChunkMapEntry.sendToPlayer(PlayerChunkMapEntry.java:176) ~[ot.class:?]
        at net.minecraft.server.management.PlayerChunkMapEntry.addPlayer(PlayerChunkMapEntry.java:74) ~[ot.class:?]
        at net.minecraft.server.management.PlayerChunkMap.addPlayer(SourceFile:227) ~[ou.class:?]
        at net.minecraft.server.management.PlayerList.preparePlayer(PlayerList.java:290) ~[pl.class:?]
        at net.minecraft.server.management.PlayerList.playerLoggedIn(PlayerList.java:378) ~[pl.class:?]
        at net.minecraft.server.management.PlayerList.initializeConnectionToPlayer(PlayerList.java:166) ~[pl.class:?]
        at shadows.fastbench.net.HijackedDedicatedPlayerList.initializeConnectionToPlayer(HijackedDedicatedPlayerList.java:19) ~[HijackedDedicatedPlayerList.class:?]
        at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.completeServerSideConnection(NetworkDispatcher.java:255) ~[NetworkDispatcher.class:?]
        at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.access$100(NetworkDispatcher.java:72) ~[NetworkDispatcher.class:?]
        at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher$1.update(NetworkDispatcher.java:205) ~[NetworkDispatcher$1.class:?]
        at net.minecraft.network.NetworkManager.processReceivedPackets(NetworkManager.java:285) ~[gw.class:?]
        at net.minecraft.network.NetworkSystem.networkTick(NetworkSystem.java:180) [oz.class:?]
        at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:790) [MinecraftServer.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:397) [nz.class:?]
        at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:668) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]