Custom vehicle prefab error

  {
      "Activate this event?": true,
      "Transport type for event (Random2Module, Random3Module, Random4Module, Module2, Module3, Module4)": "Random2Module",
      "Custom vehicle prefab (leave empty if not needed)": "assets/custom/dunebuggie.prefab",
      "Driver name (key) from driver settings in DriverController plugin": "DriverCar",
      "Companion name (key) from companion settings in DriverController plugin (list to occupy free seats in the vehicle)": [
        "Companion1",
        "Companion2"
      ],
      "Engine settings": {
        "Engine parts level (1 - 3)": 1,
        "Drop the parts when destroying vehicle?": false
      },
      "Loot container settings": {
        "Enable loot in vehicle container?": true,
        "Drop the loot when destroying the transport?": false,
        "Amount of slots": 1,
        "Name of loot set from loot settings in DriverController plugin (list loot sets for random selection)": [
          "ResourcesCar"
        ]
      },
      "Use Road Routes (has priority over off-road)": true,
      "Use Off-Road Routes (used if no road routes are available)": true,
      "Controller settings": {
        "Max speed (km/h)": 60.0,
        "Maximum speed when obstacles detected (km/h)": 5.0,
        "Chase mode settings": {
          "Chase attacking players?": true,
          "Max chase distance": 150.0,
          "Chase timer": 120.0
        }
      },
      "Turret Settings (will add the specified amount to each suitable module)": {
        "Enable Turrets on Vehicle": false,
        "Disable Turrets on Event End": true,
        "Maximum Attack Range": 50.0,
        "Player Damage Multiplier": 0.5,
        "Max turrets amount": 1,
        "At what percentage of the module's remaining health remove the turret installed on it": {
          "Min": 2.0,
          "Max": 5.0
        }
      },
      "Damage receive rate": 1.0,
      "Fuel settings": {
        "Enable automatic fuel refueling?": true,
        "Remove fuel when unlocking vehicle?": true,
        "Maximum fuel in vehicle": 500
      },
      "Vehicle headlight settings": {
        "Enable vehicle headlights?": true,
        "Use headlights only at night?": true
      },
      "Detonator settings": {
        "Add C4 to the vehicle after the death of the driver (used to despawn vehicles)": true,
        "After how many seconds explosives will be blown up": 60.0,
        "Explosives position offset": {
          "x": 0.0,
          "y": 0.8,
          "z": 0.0
        }
      }
    },

This spawns the car but no NPC's..... What did I do wrong?

Because it tries to find a vehicle module with seats. How does these custom vehicles work? I couldn't find any documentation on these

Or it tries to get mount points via BaseVehicle.mountPoints. Something is not assigned or empty, any error in the console?

Just noticed this error.

InvalidCastException: Specified cast is not valid.

I can give you Karuza's discord if you need to ask how to get them into the vehicles. 

I know they push plugins that work with he custom vehicles. So it could be a win-win.