Bukkit

[01:37:29 ERROR]: The server has stopped responding!
[01:37:29 ERROR]: Please report this to http://www.spigotmc.org/
[01:37:29 ERROR]: Be sure to include ALL relevant console errors and Minecraft crash reports
[01:37:29 ERROR]: Spigot version: git-Spigot-"8c26a90" (MC: 1.8)
[01:37:29 ERROR]: ------------------------------
[01:37:29 ERROR]: Server thread dump (Look for plugins here before reporting to Spigot!):
[01:37:29 ERROR]: ------------------------------
[01:37:29 ERROR]: Current Thread: Server thread
[01:37:29 ERROR]: PID: 16 | Suspended: false | Native: false | State: RUNNABLE
[01:37:29 ERROR]: Stack:
[01:37:29 ERROR]: java.lang.System.identityHashCode(Native Method)
[01:37:29 ERROR]: java.util.IdentityHashMap.hash(Unknown Source)
[01:37:29 ERROR]: java.util.IdentityHashMap.containsKey(Unknown Source)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:74)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:161)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:213)
[01:37:29 ERROR]: org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSerializable.representData(YamlRepresenter.java:35)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:95)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:161)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:213)
[01:37:29 ERROR]: org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSection.representData(YamlRepresenter.java:23)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:95)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:161)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:213)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:95)
[01:37:29 ERROR]: org.yaml.snakeyaml.representer.BaseRepresenter.represent(BaseRepresenter.java:65)
[01:37:29 ERROR]: org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:271)
[01:37:29 ERROR]: org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:262)
[01:37:29 ERROR]: org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:234)
[01:37:29 ERROR]: org.yaml.snakeyaml.Yaml.dump(Yaml.java:209)
[01:37:29 ERROR]: org.bukkit.configuration.file.YamlConfiguration.saveToString(YamlConfiguration.java:40)
[01:37:29 ERROR]: net.sradonia.bukkit.alphachest.Utf8YamlConfiguration.save(Utf8YamlConfiguration.java:51)
[01:37:29 ERROR]: net.sradonia.bukkit.alphachest.InventoryIO.saveToYaml(InventoryIO.java:111)
[01:37:29 ERROR]: Stack:
[01:37:29 ERROR]: sun.misc.Unsafe.park(Native Method)
[01:37:29 ERROR]: java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)
[01:37:29 ERROR]: java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(Unknown Source)
[01:37:29 ERROR]: java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(Unknown Source)
[01:37:29 ERROR]: java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(Unknown Source)
[01:37:29 ERROR]: java.util.concurrent.ThreadPoolExecutor.getTask(Unknown Source)
[01:37:29 ERROR]: java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
[01:37:29 ERROR]: java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
[01:37:29 ERROR]: java.lang.Thread.run(Unknown Source)
[01:37:29 ERROR]: ------------------------------
[01:37:29 ERROR]: Current Thread: Netty Server IO #0
[01:37:29 ERROR]: PID: 24 | Suspended: false | Native: true | State: RUNNABLE
[01:37:29 ERROR]: Thread is waiting on monitor(s):
[01:37:29 ERROR]: Locked on:sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source)
[01:37:29 ERROR]: Locked on:sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source)
[01:37:29 ERROR]: Locked on:sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source)
[01:37:29 ERROR]: Stack:
[01:37:29 ERROR]: sun.nio.ch.WindowsSelectorImpl$SubSelector.poll0(Native Method)
[01:37:29 ERROR]: sun.nio.ch.WindowsSelectorImpl$SubSelector.poll(Unknown Source)
[01:37:29 ERROR]: sun.nio.ch.WindowsSelectorImpl$SubSelector.access$400(Unknown Source)
[01:37:29 ERROR]: sun.nio.ch.WindowsSelectorImpl.doSelect(Unknown Source)
[01:37:29 ERROR]: sun.nio.ch.SelectorImpl.lockAndDoSelect(Unknown Source)
[01:37:29 ERROR]: sun.nio.ch.SelectorImpl.select(Unknown Source)
[01:37:29 ERROR]: io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:618)
[01:37:29 ERROR]: io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:306)
[01:37:29 ERROR]: io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116)
[01:37:29 ERROR]: java.lang.Thread.run(Unknown Source)
[01:37:29 ERROR]: ------------------------------
[01:37:29 ERROR]: Current Thread: Spigot Metrics Thread
[01:37:29 ERROR]: PID: 23 | Suspended: false | Native: false | State: TIMED_WAITING
[01:37:29 ERROR]: Stack:
[01:37:29 ERROR]: java.lang.Object.wait(Native Method)
[01:37:29 ERROR]: java.util.TimerThread.mainLoop(Unknown Source)
[01:37:29 ERROR]: java.util.TimerThread.run(Unknown Source)
[01:37:29 ERROR]: ------------------------------
[01:37:29 ERROR]: Current Thread: Spigot Watchdog Thread
[01:37:29 ERROR]: PID: 22 | Suspended: false | Native: false | State: RUNNABLE
[01:37:29 ERROR]: Stack:
[01:37:29 ERROR]: sun.management.ThreadImpl.dumpThreads0(Native Method)
[01:37:29 ERROR]: sun.management.ThreadImpl.dumpAllThreads(Unknown Source)
[01:37:29 ERROR]: org.spigotmc.WatchdogThread.run(WatchdogThread.java:76)
[01:37:29 ERROR]: ------------------------------

Please help me. I do not want the players to lose their chests.