Bukkit

What steps will reproduce the problem?
1. set spawnmoster flag
2. mobs continue to spawn....

What is the expected output? What do you see instead?
it must block all spawn of mobs right?

What version of the product are you using?
5.2.6

What version of the craftbukkit/bukkit are you using?
Spigot 1.8.3

Do you have an error log of what happened?
None

Please provide the result of /mw debug below:
[22:30:44 INFO]: [MultiWorld] Now printing debug information
[22:30:44 INFO]: [MultiWorld] MultiWorld version: 5.2.6
[22:30:44 INFO]: [MultiWorld] Bukkit version: git-Spigot-c3c767f-33d5de3 (MC: 1.8)
[22:30:44 INFO]: [MultiWorld]
[22:30:44 INFO]: [MultiWorld] --<[Modules]>--
[22:30:44 INFO]: [MultiWorld] [State, pluginName]
[22:30:44 INFO]: [MultiWorld] [Unloaded, EndPortalHandler]
[22:30:44 INFO]: [MultiWorld] [Unloaded, EnderChestBlokker]
[22:30:44 INFO]: [MultiWorld] [Unloaded, WorldChatSeperatorPlugin]
[22:30:44 INFO]: [MultiWorld] [Unloaded, GameModeChancer]
[22:30:44 INFO]: [MultiWorld] [Unloaded, WorldSpawnHandler]
[22:30:44 INFO]: [MultiWorld] [Unloaded, NetherPortalHandler]
[22:30:44 INFO]: [MultiWorld]
[22:30:44 INFO]: [MultiWorld] --<[CommandStacks]>--
[22:30:44 INFO]: [MultiWorld] multiworld.command.DefaultCommandStack
[22:30:44 INFO]: [MultiWorld]  - /mw []
[22:30:44 INFO]: [MultiWorld] multiworld.command.DefaultCommandStack
[22:30:44 INFO]: [MultiWorld]  - /mw [debug]

Can you try doing /mw getflag <world name> spawnmonster to verify its turned off, also, this flag won't remove any existing monsters and also doesn't block dungeon spawns