WORLDEDIT-2673 - Reported by AmAzed2025

14:23:04 [SEVERE] java.lang.UnsupportedClassVersionError: MCPCPlusXNmsBlock_147
: Unsupported major.minor version 51.0
14:23:04 [SEVERE] at java.lang.ClassLoader.defineClass1(Native Method)
14:23:04 [SEVERE] at java.lang.ClassLoader.defineClassCond(Unknown Source)

14:23:04 [SEVERE] at java.lang.ClassLoader.defineClass(Unknown Source)
14:23:04 [SEVERE] at java.lang.ClassLoader.defineClass(Unknown Source)
14:23:04 [SEVERE] at com.sk89q.worldedit.bukkit.BukkitWorld$NmsBlockClassL
oader.loadClass(BukkitWorld.java:228)
14:23:04 [SEVERE] at com.sk89q.worldedit.bukkit.BukkitWorld.(BukkitW
orld.java:146)
14:23:04 [SEVERE] at com.sk89q.worldedit.bukkit.BukkitUtil.getLocalWorld(B
ukkitUtil.java:50)
14:23:04 [SEVERE] at com.sk89q.worldedit.bukkit.BukkitPlayer.getWorld(Bukk
itPlayer.java:132)
14:23:04 [SEVERE] at com.sk89q.worldedit.bukkit.WorldEditListener.onPlayer
Interact(WorldEditListener.java:121)
14:23:04 [SEVERE] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native M
ethod)
14:23:04 [SEVERE] at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown S
ource)
14:23:04 [SEVERE] at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unkno
wn Source)
14:23:04 [SEVERE] at java.lang.reflect.Method.invoke(Unknown Source)
14:23:04 [SEVERE] at org.bukkit.plugin.java.JavaPluginLoader$1.execute(Jav
aPluginLoader.java:425)
14:23:04 [SEVERE] at org.bukkit.plugin.RegisteredListener.callEvent(Regist
eredListener.java:62)
14:23:04 [SEVERE] at org.bukkit.plugin.SimplePluginManager.fireEvent(Simpl
ePluginManager.java:477)
14:23:04 [SEVERE] at org.bukkit.plugin.SimplePluginManager.callEvent(Simpl
ePluginManager.java:462)
14:23:04 [SEVERE] at org.bukkit.craftbukkit.v1_4_R1.event.CraftEventFactor
y.callPlayerInteractEvent(CraftEventFactory.java:178)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.PlayerInteractManager.di
g(PlayerInteractManager.java:114)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.PlayerConnection.a(Playe
rConnection.java:564)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.Packet14BlockDig.handle(
SourceFile:46)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.NetworkManager.b(Network
Manager.java:290)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.PlayerConnection.d(Playe
rConnection.java:113)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.ServerConnection.b(Sourc
eFile:39)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.DedicatedServerConnectio
n.b(SourceFile:30)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.r(Minecr
aftServer.java:598)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.DedicatedServer.r(Dedica
tedServer.java:224)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.q(Minecr
aftServer.java:494)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.run(Mine
craftServer.java:427)
14:23:04 [SEVERE] at net.minecraft.server.v1_4_R1.ThreadServerApplication.
run(SourceFile:849)
14:23:04 [INFO] [WorldEdit] Using inbuilt NmsBlock for this version.
14:23:05 [INFO] /50.23.30.168:34090 lost connection

After this arrived, My world would have random mountains that are half-cut and look terrible. The biomes messed up, the world generator did also, how do I fix this?

Comment by wizjany

that actually has nothing to do with your problem, it's a harmless error
http://youtrack.sk89q.com/issue/WORLDEDIT-2652#comment=67-1680