[18:49:51 ERROR]: Couldn't save chunk; already in use by another instance of Minecraft?
net.minecraft.server.v1_11_R1.ExceptionWorldConflict: The save for world located at .\world_nether is being accessed from another location, aborting
        at net.minecraft.server.v1_11_R1.WorldNBTStorage.checkSession(WorldNBTStorage.java:78) ~[Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.World.checkSession(World.java:2807) ~[Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.ChunkRegionLoader.a(ChunkRegionLoader.java:120) ~[Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.ChunkProviderServer.saveChunk(ChunkProviderServer.java:209) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.ChunkProviderServer.unloadChunk(ChunkProviderServer.java:316) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.ChunkProviderServer.unloadChunks(ChunkProviderServer.java:268) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.WorldServer.doTick(WorldServer.java:236) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.MinecraftServer.D(MinecraftServer.java:798) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.DedicatedServer.D(DedicatedServer.java:399) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.MinecraftServer.C(MinecraftServer.java:678) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at net.minecraft.server.v1_11_R1.MinecraftServer.run(MinecraftServer.java:576) [Towny.jar:git-Spigot-3fb9445-6e3cec8]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_144]