[WARNING] Could not properly handle event PLAYER_TELEPORT

[SharkROAR]

[WARNING] Could not properly handle event PLAYER_TELEPORT:
java.lang.IllegalAccessError: Synchronized code got accessed from another thread: com.mewin.WGRegionEvents.WGRegionEventsListener$1
at org.bukkit.event.NLTCListener.onPlayerTeleport(NLTCListener:0)
at sun.reflect.GeneratedMethodAccessor48.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
at org.bukkit.craftbukkit.v1_5_R2.entity.CraftPlayer.teleport(CraftPlayer.java:371)
at org.bukkit.craftbukkit.v1_5_R2.entity.CraftEntity.teleport(CraftEntity.java:194)
at org.bukkit.command.defaults.TeleportCommand.execute(TeleportCommand.java:74)
at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:189)
at org.bukkit.craftbukkit.v1_5_R2.CraftServer.dispatchCommand(CraftServer.java:523)
at com.mewin.wgrc.RegionListener.parseCmd(RegionListener.java:65)
at com.mewin.wgrc.RegionListener.onRegionEntered(RegionListener.java:43)
at sun.reflect.GeneratedMethodAccessor52.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
at com.mewin.WGRegionEvents.WGRegionEventsListener$1.run(WGRegionEventsListener.java:160)
16:53:43 [INFO] This error is logged only once: it could have occurred multiple times by now.
16:53:43 [INFO] Potential failures may occur in other plugins handling this Event.
16:53:43 [INFO] Please contact one of the authors of plugin 'WGRegionEvents':

Happened when I jumped into a region which should teleport players back to the top when they fall.
Teleport still worked, though

[UltraMC]

Is it somehow similar to #5 ?