I spent about 12 hours over the past two days trying to isolate the plugin that was causing a NullReferenceException error.  Turns out that it is caused by the config file for Sirens.  If I do not edit the config file it is fine.  If I edit the config file it causes the error.  I just managed to get it to work with an edited config.  Here is the config file that causes the error.

{
"MountNeeded": false,
"SoundEnabled": false,
"SirenSpawnProbability": {
"MODULAR_CAR": 0.1,
"assets/rust.ai/nextai/testridablehorse.prefab": 0.0,
"assets/content/vehicles/crane_magnet/magnetcrane.entity.prefab": 0.0,
"assets/content/vehicles/minicopter/minicopter.entity.prefab": 1.0,
"assets/content/vehicles/boats/rhib/rhib.prefab": 0.1,
"assets/content/vehicles/boats/rowboat/rowboat.prefab": 0.1,
"assets/content/vehicles/sedan_a/sedantest.entity.prefab": 0.0,
"assets/content/vehicles/scrap heli carrier/scraptransporthelicopter.prefab": 1.0,
"assets/content/vehicles/workcart/workcart.entity.prefab": 0.1
},
"DefaultState": "ON"
}

Here is the config file that works

{
"MountNeeded": false,
"SoundEnabled": true,
"SirenSpawnProbability": {
"MODULAR_CAR": 0.1,
"assets/rust.ai/nextai/testridablehorse.prefab": 0.0,
"assets/content/vehicles/crane_magnet/magnetcrane.entity.prefab": 0.0,
"assets/content/vehicles/minicopter/minicopter.entity.prefab": 0.1,
"assets/content/vehicles/boats/rhib/rhib.prefab": 0.0,
"assets/content/vehicles/boats/rowboat/rowboat.prefab": 0.0,
"assets/content/vehicles/sedan_a/sedantest.entity.prefab": 0.0,
"assets/content/vehicles/scrap heli carrier/scraptransporthelicopter.prefab": 0.1,
"assets/content/vehicles/workcart/workcart.entity.prefab": 0.0
},
"DefaultState": "OFF"
}

It seems like changing the number from 0.1 to 1.0 causes the crash.

Hi there,
thank you for using the Sirens plugin and for the report.

Interesting finding. I will have a look at it.

Best regrads
ZockiRR

Actually it seems lke putting them on anything but helicopters causes the crash

Merged post

{
"MountNeeded": false,
"SoundEnabled": true,
"SirenSpawnProbability": {
"MODULAR_CAR": 0.1,
"assets/rust.ai/nextai/testridablehorse.prefab": 0.0,
"assets/content/vehicles/crane_magnet/magnetcrane.entity.prefab": 0.0,
"assets/content/vehicles/minicopter/minicopter.entity.prefab": 0.1,
"assets/content/vehicles/boats/rhib/rhib.prefab": 0.1,
"assets/content/vehicles/boats/rowboat/rowboat.prefab": 0.1,
"assets/content/vehicles/sedan_a/sedantest.entity.prefab": 0.0,
"assets/content/vehicles/scrap heli carrier/scraptransporthelicopter.prefab": 0.1,
"assets/content/vehicles/workcart/workcart.entity.prefab": 0.0
},
"DefaultState": "OFF"
}

This also causes the crash.  

This is what is says every time before the crash.  It takes about 5 minutes into loading to get the crash so its a lot of time to problem solve.  

ID In use!COBALT1
7381 / 77875
22692 / 77875
38929 / 77875
50269 / 77875
63268 / 77875
72058 / 77875
done.
Enforcing SpawnPopulation Limits
done.
Initializing 80308 entity links
50053 / 80308
65204 / 80308
70376 / 80308
NullReferenceException

{
"MountNeeded": false,
"SoundEnabled": true,
"SirenSpawnProbability": {
"MODULAR_CAR": 0.1,
"assets/rust.ai/nextai/testridablehorse.prefab": 0.0,
"assets/content/vehicles/crane_magnet/magnetcrane.entity.prefab": 0.0,
"assets/content/vehicles/minicopter/minicopter.entity.prefab": 1.0,
"assets/content/vehicles/boats/rhib/rhib.prefab": 0.0,
"assets/content/vehicles/boats/rowboat/rowboat.prefab": 0.0,
"assets/content/vehicles/sedan_a/sedantest.entity.prefab": 0.0,
"assets/content/vehicles/scrap heli carrier/scraptransporthelicopter.prefab": 1.0,
"assets/content/vehicles/workcart/workcart.entity.prefab": 0.0
},
"DefaultState": "OFF"
}

This configuration works.  So there is something wrong with boats.

Hi again,

It took some while and still I couldn't find any issue regarding the plugin which results in this error.
If you still have this problem, I will need more details about config, plugins and the specific situation.
If not, I will set this to not an issue.

Best regards
ZockiRR