No advice on how to fix this. Just chiming in to say that I’m having the same issue on my account. I thought I was just hitting the xp cap, but now it doesn’t reset even if I wait a couple of weeks between even opening the game or when I enter a new creative map.
Lengthy example:
Just played the Festival Jam Stage: Dance with Sabrina Carpenter mode. Prior to that, I played two ranked matches, and otherwise haven’t even opened the game in nearly a week. After going through her 4-song show five times, hitting all the accolades every time (including the 25 note streaks), and collecting all the coins twice, I’ve only gotten 23,658 xp total. I’m only getting 100 xp for the first star, but online other people are saying they’re getting nearly 10× what I am per accolade.