Apple Music Mixes Not Updating

My Apple Music mixes (Get up, Favorite, etc.) are not consistently updating. For example: It's been two weeks since "Get up" was updated (though it inaccurately reads as updated Monday -- two days ago), but "Favorites" was actually updated yesterday. I've an active, paid-for, subscription. The library is synced among devices. The OS is current. I've restarted devices. And yet.... Tips appreciated.