Problem/Bug My bukkit server crash when I enter or when It Start

Hello, I made a server 1.9 bukkit when I enter to it, it crash bug I stay in it, I say something in chat but the mesage dont appear this is the crash code

Code:

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 6/16/16 10:38 AM
Description: Exception ticking world

java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(Unknown Source)
    at java.util.HashMap$KeyIterator.next(Unknown Source)
    at net.minecraft.server.v1_9_R1.PlayerChunkMap.flush(PlayerChunkMap.java:119)
    at net.minecraft.server.v1_9_R1.WorldServer.doTick(WorldServer.java:244)
    at net.minecraft.server.v1_9_R1.MinecraftServer.D(MinecraftServer.java:720)
    at net.minecraft.server.v1_9_R1.DedicatedServer.D(DedicatedServer.java:361)
    at net.minecraft.server.v1_9_R1.MinecraftServer.C(MinecraftServer.java:630)
    at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:534)
    at java.lang.Thread.run(Unknown Source)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
    at java.util.HashMap$HashIterator.nextNode(Unknown Source)
    at java.util.HashMap$KeyIterator.next(Unknown Source)
    at net.minecraft.server.v1_9_R1.PlayerChunkMap.flush(PlayerChunkMap.java:119)
    at net.minecraft.server.v1_9_R1.WorldServer.doTick(WorldServer.java:244)

-- Affected level --
Details:
    Level name: world
    All players: 0 total; []
    Chunk stats: ServerChunkCache: 453 Drop: 185
    Level seed: -4441047287533866935
    Level generator: ID 00 - default, ver 1. Features enabled: false
    Level generator options: 
    Level spawn location: World: (-64,64,256), Chunk: (at 0,4,0 in -4,16; contains blocks -64,0,256 to -49,255,271), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
    Level time: 3245 game time, 3245 day time
    Level dimension: 0
    Level storage version: 0x04ABD - Anvil
    Level weather: Rain time: 29466 (now: false), thunder time: 93892 (now: false)
    Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
Stacktrace:
    at net.minecraft.server.v1_9_R1.MinecraftServer.D(MinecraftServer.java:720)
    at net.minecraft.server.v1_9_R1.DedicatedServer.D(DedicatedServer.java:361)
    at net.minecraft.server.v1_9_R1.MinecraftServer.C(MinecraftServer.java:630)
    at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:534)
    at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
    Minecraft Version: 1.9
    Operating System: Windows 10 (x86) version 10.0
    Java Version: 1.8.0_77, Oracle Corporation
    Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
    Memory: 663377832 bytes (632 MB) / 1037959168 bytes (989 MB) up to 1037959168 bytes (989 MB)
    JVM Flags: 2 total; -Xmx1024M -Xms1024M
    IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
    CraftBukkit Information: 
   Running: CraftBukkit version git-Bukkit-69e196f (MC: 1.9) (Implementing API version 1.9-R0.1-SNAPSHOT) true
   Plugins: {}
   Warnings: DEFAULT
   Reload Count: 0
   Threads: { RUNNABLE Netty Server IO #1: [sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method), sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(Unknown Source), sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(Unknown Source), sun.nio.ch.WindowsSelectorImpl.doSelect(Unknown Source), sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source), sun.nio.ch.SelectorImpl.select(Unknown Source), io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:622), io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:310), io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116), java.lang.Thread.run(Unknown Source)], RUNNABLE Server thread: [java.lang.Thread.dumpThreads(Native Method), java.lang.Thread.getAllStackTraces(Unknown Source), org.bukkit.craftbukkit.v1_9_R1.CraftCrashReport.call(CraftCrashReport.java:29), net.minecraft.server.v1_9_R1.CrashReportSystemDetails.a(SourceFile:79), net.minecraft.server.v1_9_R1.CrashReport.h(CrashReport.java:127), net.minecraft.server.v1_9_R1.CrashReport.<init>(CrashReport.java:34), net.minecraft.server.v1_9_R1.CrashReport.a(CrashReport.java:312), net.minecraft.server.v1_9_R1.MinecraftServer.D(MinecraftServer.java:722), net.minecraft.server.v1_9_R1.DedicatedServer.D(DedicatedServer.java:361), net.minecraft.server.v1_9_R1.MinecraftServer.C(MinecraftServer.java:630), net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:534), java.lang.Thread.run(Unknown Source)], WAITING Finalizer: [java.lang.Object.wait(Native Method), java.lang.ref.ReferenceQueue.remove(Unknown Source), java.lang.ref.ReferenceQueue.remove(Unknown Source), java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)], RUNNABLE Netty Server IO #0: [sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method), sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(Unknown Source), sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(Unknown Source), sun.nio.ch.WindowsSelectorImpl.doSelect(Unknown Source), sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source), sun.nio.ch.SelectorImpl.select(Unknown Source), io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:622), io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:310), io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116), java.lang.Thread.run(Unknown Source)], WAITING Chunk I/O Executor Thread-1: [sun.misc.Unsafe.park(Native Method), java.util.concurrent.locks.LockSupport.park(Unknown Source), java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(Unknown Source), java.util.concurrent.LinkedBlockingQueue.take(Unknown Source), java.util.concurrent.ThreadPoolExecutor.getTask(Unknown Source), java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source), java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source), java.lang.Thread.run(Unknown Source)], RUNNABLE Signal Dispatcher: [], BLOCKED Thread-1: [java.io.PrintStream.flush(Unknown Source), java.io.FilterOutputStream.flush(Unknown Source), org.fusesource.jansi.AnsiOutputStream.close(AnsiOutputStream.java:493), org.apache.logging.log4j.core.appender.OutputStreamManager.close(OutputStreamManager.java:138), org.apache.logging.log4j.core.appender.OutputStreamManager.releaseSub(OutputStreamManager.java:76), org.apache.logging.log4j.core.appender.AbstractManager.release(AbstractManager.java:119), org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.stop(AbstractOutputStreamAppender.java:97), org.apache.logging.log4j.core.config.BaseConfiguration.stop(BaseConfiguration.java:161), org.apache.logging.log4j.core.LoggerContext.stop(LoggerContext.java:212), org.apache.logging.log4j.core.LoggerContext$ShutdownThread.run(LoggerContext.java:437)], WAITING NonBlockingInputStreamThread: [java.lang.Object.wait(Native Method), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.run(NonBlockingInputStream.java:278), java.lang.Thread.run(Unknown Source)], TIMED_WAITING Timer-0: [java.lang.Object.wait(Native Method), java.util.TimerThread.mainLoop(Unknown Source), java.util.TimerThread.run(Unknown Source)], TIMED_WAITING Server Infinisleeper: [java.lang.Thread.sleep(Native Method), net.minecraft.server.v1_9_R1.DedicatedServer$1.run(DedicatedServer.java:56)], WAITING Reference Handler: [java.lang.Object.wait(Native Method), java.lang.Object.wait(Unknown Source), java.lang.ref.Reference.tryHandlePending(Unknown Source), java.lang.ref.Reference$ReferenceHandler.run(Unknown Source)], RUNNABLE Attach Listener: [], RUNNABLE Thread-4: [java.util.LinkedList.unlink(Unknown Source), java.util.LinkedList.remove(Unknown Source), net.minecraft.server.v1_9_R1.PlayerChunkMap.b(PlayerChunkMap.java:428), net.minecraft.server.v1_9_R1.PlayerChunk.b(PlayerChunk.java:103), net.minecraft.server.v1_9_R1.PlayerChunkMap.removePlayer(PlayerChunkMap.java:292), net.minecraft.server.v1_9_R1.PlayerList.disconnect(PlayerList.java:393), net.minecraft.server.v1_9_R1.PlayerConnection.a(PlayerConnection.java:985), net.minecraft.server.v1_9_R1.PlayerConnection.disconnect(PlayerConnection.java:241), net.minecraft.server.v1_9_R1.PlayerList.u(PlayerList.java:1268), net.minecraft.server.v1_9_R1.MinecraftServer.stop(MinecraftServer.java:451), org.bukkit.craftbukkit.v1_9_R1.util.ServerShutdownThread.run(ServerShutdownThread.java:16)], TIMED_WAITING Snooper Timer: [java.lang.Object.wait(Native Method), java.util.TimerThread.mainLoop(Unknown Source), java.util.TimerThread.run(Unknown Source)], TIMED_WAITING File IO Thread: [java.lang.Thread.sleep(Native Method), net.minecraft.server.v1_9_R1.FileIOThread.c(SourceFile:51), net.minecraft.server.v1_9_R1.FileIOThread.run(SourceFile:30), java.lang.Thread.run(Unknown Source)], RUNNABLE Thread-5: [java.io.FileOutputStream.writeBytes(Native Method), java.io.FileOutputStream.write(Unknown Source), java.io.BufferedOutputStream.flushBuffer(Unknown Source), java.io.BufferedOutputStream.flush(Unknown Source), java.io.PrintStream.write(Unknown Source), org.fusesource.jansi.AnsiOutputStream.write(AnsiOutputStream.java:82), java.io.FilterOutputStream.write(Unknown Source), java.io.PrintStream.write(Unknown Source), java.io.FilterOutputStream.write(Unknown Source), org.bukkit.craftbukkit.v1_9_R1.util.TerminalConsoleWriterThread.run(TerminalConsoleWriterThread.java:34), java.lang.Thread.run(Unknown Source)], RUNNABLE Server console handler: [org.fusesource.jansi.internal.Kernel32.ReadConsoleInputW(Native Method), org.fusesource.jansi.internal.Kernel32.readConsoleInputHelper(Kernel32.java:761), org.fusesource.jansi.internal.Kernel32.readConsoleKeyInput(Kernel32.java:794), org.fusesource.jansi.internal.WindowsSupport.readConsoleInput(WindowsSupport.java:97), org.bukkit.craftbukkit.libs.jline.WindowsTerminal.readConsoleInput(WindowsTerminal.java:215), org.bukkit.craftbukkit.libs.jline.WindowsTerminal.access$000(WindowsTerminal.java:55), org.bukkit.craftbukkit.libs.jline.WindowsTerminal$1.read(WindowsTerminal.java:157), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:169), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:137), org.bukkit.craftbukkit.libs.jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:246), org.bukkit.craftbukkit.libs.jline.internal.InputStreamReader.read(InputStreamReader.java:261), org.bukkit.craftbukkit.libs.jline.internal.InputStreamReader.read(InputStreamReader.java:198), org.bukkit.craftbukkit.libs.jline.console.ConsoleReader.readCharacter(ConsoleReader.java:2145), org.bukkit.craftbukkit.libs.jline.console.ConsoleReader.readLine(ConsoleReader.java:2349), net.minecraft.server.v1_9_R1.DedicatedServer$2.run(DedicatedServer.java:81)], RUNNABLE DestroyJavaVM: [], RUNNABLE Netty Server IO #2: [sun.misc.Unsafe.copyMemory(Native Method), io.netty.util.internal.PlatformDependent0.copyMemory(PlatformDependent0.java:307), io.netty.util.internal.PlatformDependent.copyMemory(PlatformDependent.java:343), io.netty.buffer.UnpooledUnsafeDirectByteBuf.getBytes(UnpooledUnsafeDirectByteBuf.java:280), io.netty.buffer.AbstractByteBuf.readBytes(AbstractByteBuf.java:677), io.netty.buffer.AbstractByteBuf.readBytes(AbstractByteBuf.java:684), net.minecraft.server.v1_9_R1.PacketCompressor.a(SourceFile:29), net.minecraft.server.v1_9_R1.PacketCompressor.encode(SourceFile:9), io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107), io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:658), io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:716), io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:651), io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:113), io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:658), io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:716), io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:706), io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:741), io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:895), io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:240), net.minecraft.server.v1_9_R1.NetworkManager$4.run(NetworkManager.java:190), io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:380), io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:357), io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116), java.lang.Thread.run(Unknown Source)], WAITING Server Watchdog: [java.lang.Object.wait(Native Method), java.lang.Thread.join(Unknown Source), java.lang.Thread.join(Unknown Source), java.lang.ApplicationShutdownHooks.runHooks(Unknown Source), java.lang.ApplicationShutdownHooks$1.run(Unknown Source), java.lang.Shutdown.runHooks(Unknown Source), java.lang.Shutdown.sequence(Unknown Source), java.lang.Shutdown.exit(Unknown Source), java.lang.Runtime.exit(Unknown Source), java.lang.System.exit(Unknown Source), net.minecraft.server.v1_9_R1.ThreadWatchdog.a(SourceFile:89), net.minecraft.server.v1_9_R1.ThreadWatchdog.run(SourceFile:69), java.lang.Thread.run(Unknown Source)],}
   Recent tasks from 535-565{}
    Profiler Position: N/A (disabled)
    Player Count: 0 / 20; []
    Is Modded: Definitely; Server brand changed to 'CraftBukkit'
    Type: Dedicated Server (map_server.txt)

pls help
PD: sorry because of my inglish I talk spanish

 

From what I can tell, 1.9 bukkit, and craftbukkit are very buggy. My friend tried to make a 1.9 server, and also crashed on startup. He ended up downgrading back to 1.8 after he upgraded everything to the current version.

 

thx I will do it again but in 1.8