Abb, I found one problem, it might not from your part of the mod though ...
When you start the navigation by pressing the Add Dest button (in the target screen), the HU computes the route then it will display the nav screen and immediately it speaks out the first instruction as on what to do next, if during this time, you press the on-screen mute button, you might no longer be able to bring back the voice, whatever you do (switch ON then OFF then ON etc ...).
This happens to me two or three times now ...