The key factor for me is that the times when it the display signal worked and the times when it didn't seemed completely random. I could not find any factors that influenced the success or failure. You just hit the power button and cross your fingers.
Assuming I get a replacement unit it will be interesting to see if the new one works 100% - in which case it was just a dud unit. But if the issue is still present it will be back to further investigation (or buy a Brix!)