This topic is approached in several other threads, but the ones I've looked at end up being hyperlinked to each other as if this is a GC Web issue. Some threads are trying to propose a solution which may or may not be relevant for the [current] [Android] App implementation.
In the image below, the same three completed challenges have been displayed within the area I've outlined in red for over two years now in spite of collecting hundreds of other monthly challenge badges since (e.g. October Time to Run, Halloween Walking, Active October, October weekend 10k, etc.) [but no additional weekly step challenges, for completeness]. In a perfect world, and assuming there was a wisdom to having that region in the first place, the outlined area would contain the most recent three completed challenges (including the weekly step challenge as appropriate, but excluding that if it makes the problem too hard), but in the face of scarce maintenance programmer resources, how about just eliminating that outlined section entirely? I can't imagine what processing (and its computational/database/network load) continues to isolate the three [non-consecutive] challenges shown from the multitude of other challenges I've completed, but it would almost be more 'engaging' if they were just randomly-chosen than the same stale junk from years ago.
