Problem with FlamePaper

[someonedas]

Describe the issue
[--:--:--] [Server thread/WARN]: [BedWars1058] Disabling arena: eee_test
[--:--:--] [Server thread/WARN]: java.lang.ClassCastException: class com.grinderwolf.swm.nms.v1_8_R3.CustomChunkLoader cannot be cast to class net.minecraft.server.v1_8_R3.ChunkRegionLoader (com.grinderwolf.swm.nms.v1_8_R3.CustomChunkLoader is in unnamed module of loader org.bukkit.plugin.java.PluginClassLoader @44d15579; net.minecraft.server.v1_8_R3.ChunkRegionLoader is in unnamed module of loader 'app')
[--:--:--] [Server thread/WARN]: at org.bukkit.craftbukkit.v1_8_R3.CraftServer.unloadWorld(CraftServer.java:1006)
[--:--:--] [Server thread/WARN]: at org.bukkit.craftbukkit.v1_8_R3.CraftServer.unloadWorld(CraftServer.java:967)
[--:--:--] [Server thread/WARN]: at org.bukkit.Bukkit.unloadWorld(Bukkit.java:496)
[--:--:--] [Server thread/WARN]: at com.andrei1058.bedwars.arena.mapreset.slime.SlimeAdapter.onDisable(SlimeAdapter.java:158)
[--:--:--] [Server thread/WARN]: at com.andrei1058.bedwars.arena.Arena.disable(Arena.java:1191)
[--:--:--] [Server thread/WARN]: at com.andrei1058.bedwars.BedWars.onDisable(BedWars.java:606)
[--:--:--] [Server thread/WARN]: at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:323)
[--:--:--] [Server thread/WARN]: at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:360)
[--:--:--] [Server thread/WARN]: at org.bukkit.plugin.SimplePluginManager.disablePlugin(SimplePluginManager.java:427)
[--:--:--] [Server thread/WARN]: at org.bukkit.plugin.SimplePluginManager.disablePlugins(SimplePluginManager.java:420)
[--:--:--] [Server thread/WARN]: at org.bukkit.craftbukkit.v1_8_R3.CraftServer.disablePlugins(CraftServer.java:338)
[--:--:--] [Server thread/WARN]: at net.minecraft.server.v1_8_R3.MinecraftServer.stop(MinecraftServer.java:421)
[--:--:--] [Server thread/WARN]: at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:619)
[--:--:--] [Server thread/WARN]: at java.base/java.lang.Thread.run(Thread.java:834)
Spigot version
1.8.8
Plugin version
2.2.1
How to reproduce
Make a bedwars1058 arena with a slime world, then stop the server when using flamepaper
Crash reports (if available)