Item.SetParent caused remove - this shouldn't ever happen
NullReferenceException: Object reference not set to an instance of an object
at Item.Save (System.Boolean bIncludeContainer, System.Boolean bIncludeOwners) [0x00019] in <578ce32518bb4945beb4120ca3434e21>:0
at ItemContainer.Save (System.Boolean bIncludeContainer) [0x0011c] in <578ce32518bb4945beb4120ca3434e21>:0
at PlayerInventory.SendUpdatedInventoryInternal (PlayerInventory+Type type, ItemContainer container, PlayerInventory+NetworkInventoryMode mode) [0x0002e] in <578ce32518bb4945beb4120ca3434e21>:0
at PlayerInventory.SendUpdatedInventory (PlayerInventory+Type type, ItemContainer container, System.Boolean bSendInventoryToEveryone) [0x00024] in <578ce32518bb4945beb4120ca3434e21>:0
at PlayerInventory.UpdateContainer (System.Single delta, PlayerInventory+Type type, ItemContainer container, System.Boolean bSendInventoryToEveryone, System.Single temperature) [0x00023] in <578ce32518bb4945beb4120ca3434e21>:0
at PlayerInventory.ServerUpdate (System.Single delta) [0x00045] in <578ce32518bb4945beb4120ca3434e21>:0
at PlayerInventory.MoveItem (BaseEntity+RPCMessage msg) [0x00468] in <578ce32518bb4945beb4120ca3434e21>:0
at PlayerInventory.OnRpcMessage (BasePlayer player, System.UInt32 rpc, Network.Message msg) [0x001e2] in <578ce32518bb4945beb4120ca3434e21>:0
Is all I could replicate, but it only happened when messing with coal, (bricks) unloading stack plugins to see if that helps