It happens when you try to search something.
[18:11:08] > Failed to call hook 'MarketCommand' on plugin 'ShoppyStock v1.2.7' (ArgumentException: An item with the same key has already been added. Key: attackhelicopter-0)
at System.Collections.Generic.Dictionary`2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) [0x0015a] in <8ce0bd04a7a04b4b9395538239d3fdd8>:0
at System.Collections.Generic.Dictionary`2[TKey,TValue].Add (TKey key, TValue value) [0x00000] in <8ce0bd04a7a04b4b9395538239d3fdd8>:0
at Oxide.Plugins.ShoppyStock.OpenShopUI (BasePlayer player, System.String shopName, System.String search, System.String category, System.Int32 categoryPage, System.Int32 page) [0x00d6b] in <c32ddb4e07514d8aba85a499a6476800>:0
at Oxide.Plugins.ShoppyStock.MarketCommand (BasePlayer player) [0x0013c] in <c32ddb4e07514d8aba85a499a6476800>:0
at Oxide.Plugins.ShoppyStock.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x01611] in <c32ddb4e07514d8aba85a499a6476800>:0
at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <9c80d821d00a44c9a24497c73ad2d20d>:0
at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000de] in <d646191a355d43a6b3ab36b7ee14c740>:0
at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <d646191a355d43a6b3ab36b7ee14c740>:0