I'm running into this issue with a private challenge that has ~400 books on it

I'm running into this problem with Books Removed from U.S. Naval Academy's Nimitz Library - https://app.thestorygraph.com/reading_challenges/980e7480-2967-4a7b-82bf-b0d8bbf55a6b

It has 367 books in it and it always times out. I wonder if there's a more efficient way to make it work (not loading the cover images?).

With larger challenges it's taking too long to calculate progress so it does this. I need to fix this this month. Which challenge is this?