[AlphaCommerceHub] The `RefundPayment` scenario for bank cards is broken again since 2017-12-14: «Invalid merchant»

1. Request

{
	"Header": {
		"MerchantID": "ANTERIOR001",
		"TransactionType": "RefundPayment",
		"UserID": "<...>",
		"Version": "2"
	},
	"Transaction": {
		"Amount": 169000,
		"Currency": "AUD",
		"MerchantTxnID": "1214R.783"
	}
}

2. Response

{
	"Banks": null,
	"Country": null,
	"DocumentResults": null,
	"EmailChecks": null,
	"FraudChecks": null,
	"GeoChecks": null,
	"Result": {
		"Amount": "169000",
		"Currency": "AUD",
		"custom1": null,
		"custom2": null,
		"custom3": null,
		"custom4": null,
		"custom5": null,
		"MerchantID": "ANTERIOR001",
		"MerchantTxnID": "1214R.783",
		"ResponseCode": "1028",
		"ResponseMessage": "Invalid merchant",
		"ResponseTimestamp": "14122017121710"
	},
	"ShippingService": null,
	"TaxResultLines": null
} 

The error is random.
Sometimes, a duplicate refund helps to overcome this AlphaCommerceHub’s API bug.
But be careful!
Due to its strange architecture, AlphaCommerceHub allows to refund much more money, then it was captured.
See also:

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