I think I've talked myself into this working as designed. The progress page reports the distance from your aircraft to the first waypoint, and the distances between subsequent waypoints. If you are flying away from the first waypoint, all of the distances will increase, which is what I saw the other day.
In that case though, I was flying away from the first waypoint and towards the second, which caused a little cognitive dissonance (why is the distance to the waypoint I'm flying towards increasing, not realizing until later that the distance is not the distance to the next waypoint, it's the distance from your aircraft to the first waypoint and then the second).