Cant drop Items as notOperator

I'm using Groupmanager and i have 2 world (creative) and i wont to make a third survival world and if i am a operator i can do everything and if i am not op i cant drop items(Fetching addPacket for removed entity: CraftItem) and the item dissapeares. my plugins:
TimTheEnchanter, MagicCarpet, BoatMania, MultiWorld, GroupManager, MultiInv, SafeEdit, WorldEdit, DreamLand, MinecartRevolution, MantaMobControl, SimpleCommandSigns, Vault, Stargate, bShortcut, DwarfForge, MineBackup, Permissions, CraftBookCommon, SkylandsPlus, MineralVein, BKCommonLib, Writer, GameModeChanger, CraftBookCircuits, MobArena, RebuildPlugin, NoLaggChunks, Zombes4Bukkit, Essentials, NoLaggLighting, NoLaggTNT, NoLaggItemBuffer, CraftBookMechanisms, EssentialsSpawn, NoLaggItemStacker, NoLaggMonitor, CraftBookVehicles, NoLagg, EssentialsChat
what shell i do? everybody op or everyone just member?

 

I had the same problem. I compared your plugins to mine and found that it was because of GameModeChanger. To fix this I added "gamemode.bypass.survival.drop: true" to the default permissions, and now it works properly!! Thanks, and I hope this helps you as well.