@Ian-James, map colors are limited indeed. But personally I find Dart Topographic pretty good concerning contrast. Could still be better though. I am hoping some day we will see a map-overlay feature so we can choose multiple sources of (visual) maps.
I believe I have seen multiple comments on problems for the AOCI units. It might not be the most advisable unit right now. But you can open a support ticket and attach loggings. Maybe devs can isolate the problem.
About the voice, that comes from your phone. You can choose from multiple voices and even multiple TTS packages (if there are more than one, which some Android devices have). On my own devices, I cannot say that anything sounds "robotic" at all.