For some reason NAV HUD will not always work for some firmware versions. For me in 56.x most of the times it will freeze on the first turning sign and I have to workaround this issue by going out to CMU and turn on active display Nav on and off. It also has negative implications in the sound stuttering while turning. It would be great this feature can be configured to be on and off on request, just in case it doesn't behave as it should.
Thanks.