45s and Garmin Coach PACE issues

Hi- I've started using the Garmin Coach with my Forerunner 45S. When I am actively in the workout, the main screen on my watch displays my current pace and the time remaining. However, that pace doesn't match the pace displayed on the watch face that displays distance, total time, and current pace. Sometimes the difference in pace is over 45 seconds within the moment I toggle between the watch faces. I've also noticed that the watch doesn't always notify me if I am outside of my target pace. I don't lose GPS signal along the routes, and have noticed that it struggles the most when I have to stop for a red light and that's when it seems to struggle with catching up. Does anyone know what is going on?