Pasé un día investigando este caso, pero no vi ninguna esperanza.
const Tests = (state = INIT_STATE, action) => { switch (action.type) { case GET_TEST_DETAIL: return { ...state, test: {}, error: {}, updatingTest: true, } case GET_TEST_DETAIL_SUCCESS: const test = action.payload console.log(action.payload.shortName)//has data test["shortName2"] = action.payload.shortName//has data test["shortName"] = action.payload.shortName//empty string console.log(test) return { ...state, test: test, updatingTest: false, } Ahí está la imagen capturada cuando consola.Inicie sesión en Firefox y Edge: 
No hay nada malo.
const action = { payload: { shortName: 'I am a shortname' } } const test = action.payload console.log(action.payload.shortName)//has data test["shortName2"] = action.payload.shortName//has data test["shortName"] = action.payload.shortName//empty string console.log(test)