JSON response in Datasource loop disappears after setting valid Assertion

Hi,

I am just evaluating SoapUI NG PRO / Ready API 1.9.0 with a REST webservice.

"/api/v1/exchangerates GET Request1" returns a JSON response array, and "/api/v1/exchangerates/{iso_code} GET Request1" loops though it (1.jpg). The run executes successfully. In particular, the response of every iteration is visible in the Transaction Log (2.jpg)

But after adding a JSON Existence Match Assertion which is always valid (= true), all responses become invisible (3.jpg).

Is this implemented behaviour or a bug? If the former, what's the reason?

Best,

Hans.