Type test error

Attached model is raising the following runtime error:

Error while evaluating node 'People groups': the declared result type is 'DMNType{ http://www.trisotech.com/dmn/definitions/_cbdacb7b-f72d-457d-b4f4-54020a06db24 : tListPeople }' but the actual value '[[{Age=20, Name=Ana}, {Age=22, Name=Bob}], [{Age=27, Name=Charlie}, {Age=29, Name=Daniel}], [{Age=31, Name=Edson}, {Age=32, Name=Fred}]]' is not an instance of that type

The engine should not generate such error as the type is correct.