I don't do turn by turn routing, I follow an existing track.
Normal procedure was go to "courses" and select the track. Display the track on the map (I always use black) and hit the "start/stop" button. That's all. The map centers on where I am, and I track the arrow head along my pre-defined track. When I get to my destination I have a track (I use red) to show where I actually went, which I save.
Now with 24.12 I can select a track, but as soon as I press "start", my nice black track gets wiped. GARMIN THIS IS ABSOLUTLEY A DEAL BREAKER.