Every time I turn on the server after 5-15 minutes, it crashes. Please help
[21:29:40] [Server thread/ERROR] [FML]: FMLIndexedMessageCodec exception caught
io.netty.handler.codec.EncoderException: java.lang.RuntimeException: Undefined discriminator for message type journeymap.common.network.DimensionPermissionPacket in channel jm_dim_permission
at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:106) ~[minecraft_server.1.12.2.jar:?]
at io.netty.handler.codec.MessageToMessageCodec.write(MessageToMessageCodec.java:116) ~[minecraft_server.1.12.2.jar:?]
at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738) ~[minecraft_server.1.12.2.jar:?]
at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:801) ~[minecraft_server.1.12.2.jar:?]
at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:814) ~[minecraft_server.1.12.2.jar:?]
at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:794) ~[minecraft_server.1.12.2.jar:?]
at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:831) ~[minecraft_server.1.12.2.jar:?]
at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032) ~[minecraft_server.1.12.2.jar:?]
at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296) ~[minecraft_server.1.12.2.jar:?]
at net.minecraftforge.fml.common.network.simpleimpl.SimpleNetworkWrapper.sendTo(SimpleNetworkWrapper.java:250) [SimpleNetworkWrapper.class:?]
at journeymap.common.network.PacketHandler.sendDimensionPacketToPlayer(PacketHandler.java:57) [PacketHandler.class:1.12.2-5.5.3]
at journeymap.server.events.ForgeEvents.on(ForgeEvents.java:73) [ForgeEvents.class:1.12.2-5.5.3]
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_2143_ForgeEvents_on_EntityJoinWorldEvent.invoke(.dynamic) [?:?]
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90) [ASMEventHandler.class:?]
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182) [EventBus.class:?]
at net.minecraft.world.World.func_72838_d(World.java:1206) [amu.class:?]
at net.minecraft.world.WorldServer.func_72838_d(WorldServer.java:1058) [oo.class:?]
at net.minecraft.server.management.PlayerList.func_72368_a(PlayerList.java:585) [pl.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147342_a(NetHandlerPlayServer.java:1119) [pa.class:?]
at net.minecraft.network.play.client.CPacketClientStatus.func_148833_a(SourceFile:31) [lb.class:?]
at net.minecraft.network.play.client.CPacketClientStatus.func_148833_a(SourceFile:8) [lb.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) [hv$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_144]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_144]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:723) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397) [nz.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(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_144]
Caused by: java.lang.RuntimeException: Undefined discriminator for message type journeymap.common.network.DimensionPermissionPacket in channel jm_dim_permission
at net.minecraftforge.fml.common.network.FMLIndexedMessageToMessageCodec.encode(FMLIndexedMessageToMessageCodec.java:76) ~[FMLIndexedMessageToMessageCodec.class:?]
at io.netty.handler.codec.MessageToMessageCodec$1.encode(MessageToMessageCodec.java:67) ~[minecraft_server.1.12.2.jar:?]
at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:88) ~[minecraft_server.1.12.2.jar:?]
... 29 more
[21:37:34] [Server thread/WARN] [net.minecraft.server.MinecraftServer]: Can't keep up! Did the system time change, or is the server overloaded? Running 2156ms behind, skipping 43 tick(s)