Please Help

My players are getting kicked with this message: RPC Error in MoveItem

NullReferenceException: Object reference not set to an instance of an object

at Oxide.Plugins.Skinner+BoxController.ItemRemoveCheck (Item item) [0x0027f] in <85a91cdae5bc4cb1a4566cab8807b462>:0

at Oxide.Plugins.Skinner+BoxController.CheckforItem (Item item, System.Boolean b) [0x0013e] in <85a91cdae5bc4cb1a4566cab8807b462>:0

at ItemContainer.Remove (Item item) [0x00058] in <be4adbdf5e0f4c4e9c1c34c20f6b5421>:0

at Item.SetParent (ItemContainer target) [0x00012] in <be4adbdf5e0f4c4e9c1c34c20f6b5421>:0

at Item.RemoveFromContainer () [0x00009] in <be4adbdf5e0f4c4e9c1c34c20f6b5421>:0

at Item.MoveToContainer (ItemContainer newcontainer, System.Int32 iTargetPos, System.Boolean allowStack, System.Boolean ignoreStackLimit, BasePlayer sourcePlayer, System.Boolean allowSwap) [0x005f9] in <be4adbdf5e0f4c4e9c1c34c20f6b5421>:0

at PlayerInventory.MoveItem (BaseEntity+RPCMessage msg) [0x0049d] in <be4adbdf5e0f4c4e9c1c34c20f6b5421>:0

at PlayerInventory.OnRpcMessage (BasePlayer player, System.UInt32 rpc, Network.Message msg) [0x001e4] in <be4adbdf5e0f4c4e9c1c34c20f6b5421>:0

UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)

UnityEngine.DebugLogHandler:LogException(Exception, Object)

UnityEngine.Logger:LogException(Exception, Object)

UnityEngine.Debug:LogException(Exception)

PlayerInventory:OnRpcMessage(BasePlayer, UInt32, Message)

BaseEntity:SV_RPCMessage(UInt32, Message)

ServerMgr:OnRPCMessage(Message)

ServerMgr:OnNetworkMessage(Message)

Facepunch.Network.Raknet.Server:ProcessRead(NetRead)

Network.BaseNetwork:Cycle()

MonoMod.Utils.DynamicMethodDefinition:ServerMgr.Update_Patch0(ServerMgr)