Not getting international result for certain weight??

I’m quite confused as to what might be happening here. I’m trying to get shipping quotes for a package to Australia. We only have POS Indonesia available for international (and domestic).

When I turn on debugging and put through this order, I don’t seem to be getting “EMS BARANG” results (which I believe is POS Indonesia international):

{
	"calculate_shipping.$api_request_data": {
		"zone": "international",
		"params": {
			"origin": 128,
			"destination": 9,
			"width": 0,
			"length": 0,
			"height": 0,
			"weight": 154,
			"courier": [
				"pos"
			]
		}
	}
}

Result:

{
	"calculate_shipping.$results.parsed": [
		{
			"service": "PAKETPOS BIASA LN",
			"description": "",
			"cost": 266067,
			"currency": "IDR",
			"etd": "60 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		},
		{
			"service": "POS EKSPOR",
			"description": "",
			"cost": 316356,
			"currency": "IDR",
			"etd": "5 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		}
	]
}

But when I increase the quantity of one of those products, causing a rise in weight, I get much more results, including “EMS Barang”:

{
	"calculate_shipping.$api_request_data": {
		"zone": "international",
		"params": {
			"origin": 128,
			"destination": 9,
			"width": 0,
			"length": 0,
			"height": 0,
			"weight": 192,
			"courier": [
				"pos"
			]
		}
	}
}

The results:

{
	"calculate_shipping.$results.parsed": [
		{
			"service": "R LN",
			"description": "",
			"cost": 154683,
			"currency": "IDR",
			"etd": "8 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		},
		{
			"service": "EMS BARANG",
			"description": "",
			"cost": 293190,
			"currency": "IDR",
			"etd": "3 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		},
		{
			"service": "PAKETPOS CEPAT LN",
			"description": "",
			"cost": 938208,
			"currency": "IDR",
			"etd": "8 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		},
		{
			"service": "PAKETPOS BIASA LN",
			"description": "",
			"cost": 271035,
			"currency": "IDR",
			"etd": "60 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		},
		{
			"service": "ePacket LP APP",
			"description": "",
			"cost": 157716,
			"currency": "IDR",
			"etd": "8 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		},
		{
			"service": "POS EKSPOR",
			"description": "",
			"cost": 349806,
			"currency": "IDR",
			"etd": "5 days",
			"note": "",
			"cost_conversion": false,
			"courier": "pos"
		}
	]
}

Why would the simple difference in weight be causing this?