Failed to call hook 'OnHelicopterDropCrate' on plugin 'GUIAnnouncements v2.0.3' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.GUIAnnouncements.OnHelicopterDropCrate (CH47HelicopterAIController heli) [0x00016] in :0 
  at Oxide.Plugins.GUIAnnouncements.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00af2] in :0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in :0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in :0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in :0 

I am at the latest updates for steam and Umod. 

{
  "A List Of Available Colors To Use (DO NOT CHANGE)": {
    "Banner Colors": "Grey, Red, Orange, Yellow, Green, Cyan, Blue, Purple",
    "Text Colors": "White, Red, Orange, Yellow, Green, Cyan, Blue, Purple"
  },
  "General Settings": {
    "Adjust Vertical Position": 0.0,
    "Announcement Duration": 10.0,
    "Fade In Time": 0.5,
    "Fade Out Time": 0.5,
    "Font Size": 18
  },
  "Private New Player Announcements": {
    "Announcements List (Show On This Many Joins : List To Show)": {
      "1": [
        "1st Join {rank} {playername} Welcome to Darklabs don't forget to join our Discord! For a list of game commands!",
        "1st Join {rank} {playername} Welcome to Darklabs.",
        "1st Join {rank} {playername} If you have any issues please do /calladmin."
      ],
      "2": [
        "2nd Join {rank} {playername} Welcome to Darklabs! Check out our donator section on Discord",
        "2nd Join {rank} {playername} Don't forget to check out the commands shortcut list on Discord",
        "2nd Join {rank} {playername} Report Cheaters by doing /report player was flying."
      ],
      "3": [
        "3rd Join {rank} {playername} If you enjoy our server please support our work by becoming a donator! :)",
        "3rd Join {rank} {playername} Updates frequently with new features and fixes.",
        "3rd Join {rank} {playername} If you have any issues please do /calladmin."
      ]
    },
    "Banner Color": "Blue",
    "Enabled": true,
    "Text Color": "Red"
  },
  "Private Respawn Announcements": {
    "Announcements List": [
      "{playername} Respawn announcement 1.",
      "{playername} Respawn announcement 2.",
      "{playername} Respawn announcement 3."
    ],
    "Banner Color": "Grey",
    "Enabled": false,
    "Text Color": "White"
  },
  "Private Test Announcement": {
    "Adjust Vertical Position": 0.0,
    "Banner Color": "Grey",
    "Duration": 10.0,
    "Fade In Time": 0.5,
    "Fade Out Time": 0.5,
    "Font Size": 18,
    "Text Color": "White"
  },
  "Private Welcome Announcements": {
    "Banner Color": "Grey",
    "Delay": 0.0,
    "Duration": 20.0,
    "Enabled": true,
    "Show Welcome Back If Player Has Been Here Before": true,
    "Text Color": "White",
    "Welcome Back Text": "Welcome back {playername}! There are {playercount} player(s) online.",
    "Welcome Text": "Welcome {playername}! There are {playercount} player(s) online."
  },
  "Public Airdrop Announcements": {
    "Banner Color": "Green",
    "Enabled": true,
    "Show Location": false,
    "Text": "Airdrop en route!",
    "Text Color": "Yellow",
    "Text With Grid": "Airdrop en route to {grid}."
  },
  "Public Automatic Game Time Announcements": {
    "Announcement List (Show at this in game time : Announcements to show)": {
      "18:15": [
        "The in game time is 18:15 announcement 1.",
        "The in game time is 18:15 announcement 2.",
        "The in game time is 18:15 announcement 3."
      ],
      "00:00": [
        "The in game time is 00:00 announcement 1.",
        "The in game time is 00:00 announcement 2.",
        "The in game time is 00:00 announcement 3."
      ],
      "12:00": [
        "The in game time is 12:00 announcement 1.",
        "The in game time is 12:00 announcement 2.",
        "The in game time is 12:00 announcement 3."
      ]
    },
    "Banner Color": "Grey",
    "Enabled": true,
    "Text Color": "White"
  },
  "Public Automatic Real Time Announcements": {
    "Announcement List (Show at this local time : Announcements to show)": {
      "18:15": [
        "The local time is 18:15 announcement 1.",
        "The local time is 18:15 announcement 2.",
        "The local time is 18:15 announcement 3."
      ],
      "00:00": [
        "The local time is 00:00 announcement 1.",
        "The local time is 00:00 announcement 2.",
        "The local time is 00:00 announcement 3."
      ],
      "12:00": [
        "The local time is 12:00 announcement 1.",
        "The local time is 12:00 announcement 2.",
        "The local time is 12:00 announcement 3."
      ]
    },
    "Banner Color": "Grey",
    "Enabled": false,
    "Text Color": "White"
  },
  "Public Automatic Timed Announcements": {
    "Announcement List": [
      [
        "1st Automatic Timed Announcement 1",
        "1st Automatic Timed Announcement 2"
      ],
      [
        "2nd Automatic Timed Announcement 1",
        "2nd Automatic Timed Announcement 2"
      ],
      [
        "3rd Automatic Timed Announcement 1",
        "3rd Automatic Timed Announcement 2"
      ]
    ],
    "Banner Color": "Grey",
    "Enabled": false,
    "Show Every (HH:MM:SS)": "00:30:00",
    "Text Color": "White"
  },
  "Public Bradley APC Announcements": {
    "Destroyed": false,
    "Destroyed Banner Color": "Red",
    "Destroyed Text": "The APC has been destroyed.",
    "Destroyed Text Color": "White",
    "Destroyed With Destroyer Text": "{playername} got the last shot on the APC destroying it!",
    "Show Destroyer": false,
    "Spawn": false,
    "Spawn Banner Color": "Red",
    "Spawn Text": "An APC is patrolling the launch site!",
    "Spawn Text Color": "Yellow"
  },
  "Public Cargoship Announcements": {
    "Leave": true,
    "Leave Banner Color": "Blue",
    "Leave Text": "The cargoship is departing.",
    "Leave Text Color": "White",
    "Spawn": true,
    "Spawn Banner Color": "Blue",
    "Spawn Text": "Cargoship ahoy!",
    "Spawn Text Color": "Yellow"
  },
  "Public Chinook Announcements": {
    "Announce Crate Drops": true,
    "Crate Dropped Banner Color": "Red",
    "Crate Dropped Text": "The Chinook has dropped a crate!",
    "Crate Dropped Text Color": "Yellow",
    "Crate Dropped Text With Grid": "The Chinook has dropped a crate in {grid}.",
    "Despawn": true,
    "Despawn Banner Color": "Red",
    "Despawn Text": "The Chinook has left.",
    "Despawn Text Color": "White",
    "Destroyed": true,
    "Destroyed Banner Color": "Red",
    "Destroyed Text": "The Chinook has been taken down!",
    "Destroyed Text Color": "White",
    "Destroyed Text With Destroyer": "{playername} got the last shot on the Chinook taking it down!",
    "Show Crate Drop Location": true,
    "Show Destroyer": false,
    "Spawn": true,
    "Spawn Banner Color": "Red",
    "Spawn Text": "Chinook inbound!",
    "Spawn Text Color": "Yellow"
  },
  "Public Christmas Stocking Refill Announcement": {
    "Banner Color": "Green",
    "Enabled": false,
    "Text": "Santa has refilled your stockings. Go check what you've got!",
    "Text Color": "Red"
  },
  "Public Helicopter Announcements": {
    "Despawn": false,
    "Despawn Banner Color": "Red",
    "Despawn Text": "The patrol helicopter has left.",
    "Despawn Text Color": "White",
    "Destroyed": false,
    "Destroyed Banner Color": "Red",
    "Destroyed Text": "The patrol helicopter has been taken down!",
    "Destroyed Text Color": "White",
    "Destroyed Text With Destroyer": "{playername} got the last shot on the helicopter taking it down!",
    "Show Destroyer": false,
    "Spawn": false,
    "Spawn Banner Color": "Red",
    "Spawn Text": "Patrol Helicopter Inbound!",
    "Spawn Text Color": "Orange"
  },
  "Public Join/Leave Announcements": {
    "Announce Only Players With Permission": true,
    "Join Banner Color": "Grey",
    "Join Enabled": true,
    "Join Text": "{rank} {playername} has joined.",
    "Join Text Color": "White",
    "Leave Banner Color": "Grey",
    "Leave Enabled": true,
    "Leave Text": "{rank} {playername} has left.",
    "Leave Text Color": "White"
  },
  "Public Oil Rig Crate Hack Announcements": {
    "Banner Color": "Orange",
    "Enabled": false,
    "Hack Text": "An oil rig crate is being hacked!",
    "Hack Text With Large Oil Rig": "The large oil rig crate is being hacked!",
    "Hack Text With Small Oil Rig": "The small oil rig crate is being hacked!",
    "Specify Which Oil Rig": false,
    "Text Color": "Yellow"
  },
  "Public Player Banned Announcement": {
    "Banner Color": "Grey",
    "Enabled": false,
    "Text": "{playername} has been banned. {reason}.",
    "Text Color": "Red"
  },
  "Public Restart Announcements": {
    "Announce With Time Left (HH:MM:SS)": [
      "12:00:00",
      "11:00:00",
      "10:00:00",
      "09:00:00",
      "08:00:00",
      "07:00:00",
      "06:00:00",
      "05:00:00",
      "04:00:00",
      "03:00:00",
      "02:00:00",
      "01:00:00",
      "00:45:00",
      "00:30:00",
      "00:15:00",
      "00:05:00"
    ],
    "Banner Color": "Grey",
    "Cancelled Scheduled Restart Text": "The restart in {time} has been cancelled.",
    "Enabled": true,
    "Restart Announcement Text": "Restarting in {time}",
    "Restart At (HH:MM:SS)": [
      "08:00:00",
      "20:00:00"
    ],
    "Restart My Server": true,
    "Suspended Restart Text": "The restart in {time} has been suspended.",
    "Text Color": "White"
  },
  "Third Party Plugin Support": {
    "Do Not Overlay LustyMap": false,
    "LustyMap Position (Left/Right)": "Left"
  }
}

Current Config. 

Current Active Plugin list 122:

Thanks for the info.

If you could recreate it that would be a massive help in understanding the behaviour. Might be worth starting with MyCH47 to see if it is something players would be doing with that?

The deepwater Rig event over on chaos code is the one it appears to error out on every time it runs. 

Ok so that plugin is doing something with calling the OnHelicopterDropCrate hook for some reason and it is missing data, hence why it triggers the call on my plugin which tries to use missing data and produces the NRE.

There's not really anything I can do about that, though it won't affect the functionality of the plugin.