服务器为1.12.2 paper端
Couldn't save chunk; already in use by another instance of Minecraft?
net.minecraft.server.v1_12_R1.ExceptionWorldConflict: Failed to check session lock for world located at .\DXL_Game_0, aborting. Stop the server and delete the session.lock in this world to prevent further issues.
        at net.minecraft.server.v1_12_R1.WorldNBTStorage.checkSession(WorldNBTStorage.java:85) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.World.checkSession(World.java:3003) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.ChunkRegionLoader.saveChunk(ChunkRegionLoader.java:138) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.ChunkProviderServer.saveChunk(ChunkProviderServer.java:257) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.ChunkProviderServer.unloadChunk(ChunkProviderServer.java:416) ~[Paper-1.12.2.jar:git-Paper-1574]
        at org.bukkit.craftbukkit.v1_12_R1.CraftWorld.lambda$unloadChunk0$0(CraftWorld.java:255) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.MCUtil.ensureMain(MCUtil.java:69) ~[Paper-1.12.2.jar:git-Paper-1574]
        at org.bukkit.craftbukkit.v1_12_R1.CraftWorld.unloadChunk0(CraftWorld.java:248) ~[Paper-1.12.2.jar:git-Paper-1574]
        at org.bukkit.craftbukkit.v1_12_R1.CraftWorld.unloadChunk(CraftWorld.java:244) ~[Paper-1.12.2.jar:git-Paper-1574]
        at org.bukkit.craftbukkit.v1_12_R1.CraftWorld.unloadChunk(CraftWorld.java:217) ~[Paper-1.12.2.jar:git-Paper-1574]
        at org.bukkit.craftbukkit.v1_12_R1.CraftChunk.unload(CraftChunk.java:140) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.dmulloy2.nospawnchunks.NoSpawnChunks.unloadChunks(NoSpawnChunks.java:171) ~[?:?]
        at net.dmulloy2.nospawnchunks.NoSpawnChunks$1UnloadLaterTask.run(NoSpawnChunks.java:187) ~[?:?]
        at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftTask.run(CraftTask.java:63) ~[Paper-1.12.2.jar:git-Paper-1574]
        at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:423) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:840) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:423) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:774) ~[Paper-1.12.2.jar:git-Paper-1574]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:666) ~[Paper-1.12.2.jar:git-Paper-1574]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_271]

dxl报错是因为你回收区块的插件没找到这个世界 去改改你回收区块的插件就能解决了

感谢大佬！！！！！！！！！！