Lumen validation rules not working for optional fields

Question

I'm trying to validate this request payloads:

Case 1:

{
    "products": [],
    "suppliers": ["supplier hash"]
}

Case 2:

{
    "products": [],
    "withinDeliveryRange": {
        "distance": 50,
        "postalCode": "85012"
    },
}

Case 3:

{
    "products": [],
    "suppliers": ["supplier hash"],
    "withinDeliveryRange": {
        "distance": 50,
        "postalCode": "85012"
    },
}

Case 4:

{
    "products": [],
    "suppliers": ["supplier hash"],
    "withinDeliveryRange": {
        "distance": 50,
        "postalCode": "85012"
    },
}

This my validation rules:

$this->validate(
    $_request,
    [
        'products' => 'array|nullable',
        'suppliers' => 'required_unless:withinDeliveryRange,null|array|nullable',
        'withinDeliveryRange' => 'required_unless:suppliers,null|array:distance,postalCode|nullable',
    ]
);

I'm expecting all cases to pass the validation, except the case 4 when we don't provide any of them, however:

• case 1: passes
• case 2: fails
• case 3: passes
• case 4: fails

The case 2 fails and the rule for withinDeliveryRange should work as for suppliers does, it's kind weird too because sometimes this case 2 passes but most of the times it fails.

Error message:

{"suppliers":["The suppliers field is required unless within delivery range is in null."]}

Are my rules correct? what should I change or maybe another rules fits better for this scenario.