Server crashes every now and then

Hi, for the last day I have had problems with server crashing.Every now and then it would unexpectedly crash or lag for a minute or two.Any help please?
Here is what the console gets when the server is about to crash

crash (open) crash (close)

28.06 12:10:23 [Server] INFO Player tabby3000 used command: /chairs reload
28.06 12:10:23 [Server] INFO Sitting packet byte: 4
28.06 12:10:23 [Server] INFO Allowed block: WOOD_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: SPRUCE_WOOD_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: JUNGLE_WOOD_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: BIRCH_WOOD_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: SANDSTONE_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: COBBLESTONE_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: BRICK_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: SMOOTH_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: NETHER_BRICK_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] INFO Allowed block: QUARTZ_STAIRS => 0.7 => 0
28.06 12:10:23 [Server] SEVERE null
28.06 12:10:23 [Server] INFO org.bukkit.command.CommandException: Unhandled exception executing command 'chairs' in plugin Chairs v2.1.4c
28.06 12:10:23 [Server] INFO at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46)
28.06 12:10:23 [Server] INFO at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:189)
28.06 12:10:23 [Server] INFO at org.bukkit.craftbukkit.v1_5_R3.CraftServer.dispatchCommand(CraftServer.java:546)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.PlayerConnection.handleCommand(PlayerConnection.java:979)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.PlayerConnection.chat(PlayerConnection.java:895)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.PlayerConnection.a(PlayerConnection.java:840)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.Packet3Chat.handle(Packet3Chat.java:44)
28.06 12:10:23 [Server] INFO at org.spigotmc.netty.NettyNetworkManager.b(NettyNetworkManager.java:218)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.PlayerConnection.d(PlayerConnection.java:109)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.ServerConnection.b(SourceFile:35)
28.06 12:10:23 [Server] INFO at org.spigotmc.MultiplexingServerConnection.b(MultiplexingServerConnection.java:72)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:583)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:227)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:472)
28.06 12:10:23 [Server] INFO at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:404)

Thank you

 

@Alexei17 Just remove your chairs plugin or update it

 

Removed.Still crashes.

 

Can we have a new crash log or something in pastebin ?
@Alexei17