When parsing the vehicles array in the json input, we loop over vehicles and use check_id which throws whenever encountering a non-object (e.g. a string). As a result, this kind of input is normally handled as an input error:

{
  "vehicles": [
    {
      "id": 1,
      "capacity": [14],
      ...
    },
    "foo"
  ],
  ...
}

Now the fun fact is that if we exchange order for the first two values in vehicles, we hit a Rapidjson assert related to "foo" not being an object.

This is due to an earlier call to get_amount_size which tries to access the capacity value without prior check for having a valid json object.

Extra bonus fixing point: inline get_amount_size and get rid of the loop on vehicles, it's not necessary because we enforce amount size consistency down the line when adding vehicles/jobs.