Pex crashes all the time and causes lag / crash

hello

someone know how to fix this error ?

15:54:48
CONSOLE:
[WARNING] [Server] The main thread failed to respond after 10 seconds
15:54:48
CONSOLE:
[WARNING] [Server] Probable Plugin causes: 'PermissionsEx, Vault and ServerSigns'
15:54:48
CONSOLE:
[WARNING] [Server] What follows is the stack trace of the main thread
15:54:48
CONSOLE:
[WARNING] [Server] at java.util.HashMap.hash(HashMap.java:351)
15:54:48
CONSOLE:
[WARNING] [Server] at java.util.HashMap.put(HashMap.java:471)
15:54:48
CONSOLE:
[WARNING] [Server] at java.util.HashSet.add(HashSet.java:217)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serializeNode(Serializer.java:170)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serializeNode(Serializer.java:191)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serializeNode(Serializer.java:207)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serializeNode(Serializer.java:207)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serializeNode(Serializer.java:207)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serializeNode(Serializer.java:207)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serializeNode(Serializer.java:207)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.serializer.Serializer.serialize(Serializer.java:112)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:271)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:261)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:233)
15:54:48
CONSOLE:
[WARNING] [Server] at org.yaml.snakeyaml.Yaml.dump(Yaml.java:209)
15:54:48
CONSOLE:
[WARNING] [Server] at org.bukkit.configuration.file.YamlConfiguration.saveToString(YamlConfiguration.java:38)
15:54:48
CONSOLE:
[WARNING] [Server] at org.bukkit.configuration.file.FileConfiguration.save(FileConfiguration.java:54)
15:54:48
CONSOLE:
[WARNING] [Server] at ru.tehkode.permissions.backends.FileBackend.save(FileBackend.java:282)
15:54:48
CONSOLE:
[WARNING] [Server] at ru.tehkode.permissions.backends.file.FileEntity.save(FileEntity.java:215)
15:54:48
CONSOLE:
[WARNING] [Server] at ru.tehkode.permissions.backends.file.FileEntity.setPermissions(FileEntity.java:98)
15:54:48
CONSOLE:
[WARNING] [Server] at ru.tehkode.permissions.ProxyPermissionUser.setPermissions(ProxyPermissionUser.java:92)
15:54:48
CONSOLE:
[WARNING] [Server] at ru.tehkode.permissions.PermissionUser.addPermission(PermissionUser.java:707)
15:54:48
CONSOLE:
[WARNING] [Server] at net.milkbowl.vault.permission.plugins.Permission_PermissionsEx.playerAdd(Permission_PermissionsEx.java:142)
15:54:48
CONSOLE:
[WARNING] [Server] at net.milkbowl.vault.permission.Permission.playerAdd(Permission.java:189)
15:54:48
CONSOLE:
[WARNING] [Server] at de.czymm.ServerSigns.tasks.CommandTask.run(CommandTask.java:45)
15:54:48
CONSOLE:
[WARNING] [Server] at org.bukkit.craftbukkit.v1_5_R3.scheduler.CraftTask.run(CraftTask.java:53)
15:54:48
CONSOLE:
[WARNING] [Server] at org.bukkit.craftbukkit.v1_5_R3.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345)
15:54:48
CONSOLE:
[WARNING] [Server] at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:513)
15:54:48
CONSOLE:
[WARNING] [Server] at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:226)
15:54:48
CONSOLE:
[WARNING] [Server] at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:477)
15:54:48
CONSOLE:
[WARNING] [Server] at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:410)
15:54:48
CONSOLE:
[WARNING] [Server] at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)
15:54:48
CONSOLE:
[INFO] Read timed out
15:54:52
CONSOLE:
[WARNING] [Server] The main thread is still stuck, current loop line is:
15:54:52
CONSOLE:
[WARNING] [Server] at org.bukkit.craftbukkit.v1_5_R3.scheduler.CraftTask.run(CraftTask.java:53)
15:54:52
CONSOLE:
[WARNING] [Server] This appears to be plugin 'PermissionsEx'!

 

[WARNING] [Server] This appears to be plugin 'PermissionsEx'!

Read the error.

 

Where's that document about PEX when you need it...

 

Well whats the problem then .. i cant find it