[HolographicDisplays] Unhandled exception occured in onPacketSending(PacketEvent) for HolographicDisplays
java.lang.IllegalStateException: Not implemented
        at com.gmail.filoghost.holographicdisplays.nms.interfaces.NMSManager.getEntityFromID(NMSManager.java:42) ~[HolographicDisplays%20(1).jar:?]
        at com.gmail.filoghost.holographicdisplays.bridge.protocollib.current.ProtocolLibHookImpl.getEntity(ProtocolLibHookImpl.java:189) ~[HolographicDisplays%20(1).jar:?]
        at com.gmail.filoghost.holographicdisplays.bridge.protocollib.current.ProtocolLibHookImpl.access$000(ProtocolLibHookImpl.java:55) ~[HolographicDisplays%20(1).jar:?]
        at com.gmail.filoghost.holographicdisplays.bridge.protocollib.current.ProtocolLibHookImpl$1.onPacketSending(ProtocolLibHookImpl.java:144) ~[HolographicDisplays%20(1).jar:?]
        at com.comphenix.protocol.injector.SortedPacketListenerList.invokeSendingListener(SortedPacketListenerList.java:195) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.SortedPacketListenerList.invokePacketSending(SortedPacketListenerList.java:149) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.PacketFilterManager.handlePacket(PacketFilterManager.java:588) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.PacketFilterManager.invokePacketSending(PacketFilterManager.java:564) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.ProtocolInjector.packetQueued(ProtocolInjector.java:336) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.ProtocolInjector.onPacketSending(ProtocolInjector.java:298) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector.processSending(ChannelInjector.java:378) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector.access$800(ChannelInjector.java:64) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector$3.handleScheduled(ChannelInjector.java:343) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.ChannelInjector$3.onMessageScheduled(ChannelInjector.java:313) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.ChannelProxy$2.schedulingRunnable(ChannelProxy.java:127) [ProtocolLib.jar:4.5.1]
        at com.comphenix.protocol.injector.netty.EventLoopProxy.execute(EventLoopProxy.java:95) [ProtocolLib.jar:4.5.1]
        at net.minecraft.server.v1_12_R1.NetworkManager.a(NetworkManager.java:194) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.NetworkManager.sendPacket(NetworkManager.java:143) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.PlayerConnection.sendPacket(PlayerConnection.java:1140) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.EntityTrackerEntry.broadcast(EntityTrackerEntry.java:292) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.EntityTrackerEntry.broadcastIncludingSelf(EntityTrackerEntry.java:298) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.EntityTrackerEntry.d(EntityTrackerEntry.java:265) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.EntityTrackerEntry.track(EntityTrackerEntry.java:207) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.EntityTracker.updatePlayers(EntityTracker.java:182) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:834) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [spigot-1.12.2.jar:git-Spigot-dcd1643-e60fc34]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_161]
[12:08:52 ERROR]: Parameters:
  net.minecraft.server.v1_12_R1.PacketPlayOutEntityMetadata@1ce654[
    a=383
    b=[net.minecraft.server.v1_12_R1.DataWatcher$Item@645becc6]

尝试升级protocollib

我这是最新版 spigot下的

行啊，很棒啊。试试用开发版：
ProtocolLib-4.4.0:https://ci.codemc.io/job/ThirdPa ... get/ProtocolLib.jar

HolographicDisplays:https://ci.codemc.io/job/filogho ... -2.4.5-SNAPSHOT.jar

插件去年发的 都没更新