Nissan Navara D40 ST 2013: Problems between 3rd and 4th

I bought a new Nissan Navara D40 ST automatic in January of this year. I have been experiencing a problem between third and fourth gear where it revs to a point and then drops before continuing on to fourth. It feels like the torque converter is not locking up. I have spoken to a couple of other people who have the same issue. My dealer told me that they had experienced this, but Nissan was not identifying it as a problem. Nissan's customer service people told me that these cars were not specifically designed for Australia and what I was experiencing may be a "characteristic of the car". I asked what it would take for Nissan to address the problem and she said 'If there is an actual problem Nissan would consider investigating but that is not the case here". I'm a little bit annoyed because this is my first new car and I went for the Navara because of its reputation and popularity. Have you heard of this issue and can it be rectified?