im getting this error when u se /npc_reset and it also dose not delete the npc

Failed to call hook 'cmdChatNPCReset' on plugin 'HumanNPC v0.3.47' (ArgumentException: An item with the same key has alr
eady been added. Key: rifle.ak)
  at System.Collections.Generic.Dictionary`2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.
InsertionBehavior behavior) [0x000c1] in <fb001e01371b4adca20013e0ac763896>:0                       1kb/s in, 7kb/s out
  at System.Collections.Generic.Dictionary`2[TKey,TValue].Add (TKey key, TValue value) [0x00000] in <fb001e01371b4adca20
013e0ac763896>:0
  at Oxide.Plugins.HumanNPC.OnServerInitialized () [0x00117] in <73cb9ddef9784b11a1b27f0b0d6eee8f>:0
  at Oxide.Plugins.HumanNPC.cmdChatNPCReset (BasePlayer player, System.String command, System.String[] args) [0x00068] i
n <73cb9ddef9784b11a1b27f0b0d6eee8f>:0
  at Oxide.Plugins.HumanNPC.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x0115f] in <
73cb9ddef9784b11a1b27f0b0d6eee8f>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <
80b90e8213db44b29ec2d4111764172c>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <ec05e0208c9149bba43
236ca58fea105>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <ec05e0208c9149bba43236c
a58fea105>:0​

Whenever I put the /npc_reset command in the npc remains and isn't interactable, plugin reports there are no NPCs.
Seems like it has something to do with the snowball gun?
Whenever I use the command it gives me:

Failed to call hook 'cmdChatNPCReset' on plugin 'HumanNPC v0.3.47' (ArgumentException: An item with the same key has already been added. Key: snowballgun)
  at System.Collections.Generic.Dictionary`2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) [0x000c1] in <fb001e01371b4adca20013e0ac763896>:0
  at System.Collections.Generic.Dictionary`2[TKey,TValue].Add (TKey key, TValue value) [0x00000] in <fb001e01371b4adca20013e0ac763896>:0
  at Oxide.Plugins.HumanNPC.OnServerInitialized () [0x00117] in <680e0ccddb0c4eb7b8eb8c43a1833ddc>:0
  at Oxide.Plugins.HumanNPC.cmdChatNPCReset (BasePlayer player, System.String command, System.String[] args) [0x00068] in <680e0ccddb0c4eb7b8eb8c43a1833ddc>:0
  at Oxide.Plugins.HumanNPC.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x0115f] in <680e0ccddb0c4eb7b8eb8c43a1833ddc>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <80b90e8213db44b29ec2d4111764172c>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <ec05e0208c9149bba43236ca58fea105>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <ec05e0208c9149bba43236ca58fea105>:0