When the problem is not clear cut, it is difficult for us at the factory to determine what we should do, especially when there is a distributor involve. If you are a USA customer, we would have ship you a replacement unit long ago. But shipping to South Africa is extremely expensive.
So the resolution for your situation is very simple as you have stated: your distributor has one unit and you claimed that your unit behaves differently - so you bring your unit to the distributor and compare both with the problem that you stated (If it is a power supply failure, or some channels failed to produce sound, that's easy to determine but certain software feature that doesn't work, that's strange).
Then your distributor can simply tell us: "Yes, I have seen it, however unlikely, they do behave differently."
And we will ship a replacement unit or board to your distributor with his next order.
By the way, please check that your firmware version is 2.5.