Same problem for another movie:

On the page of the " Naked Weapon (2002) " movie ( https://www.themoviedb.org/movie/10855-chek-law-dak-gung?language=en-US ), this movie is indicated as being part of the "Naked Collection" set ( https://www.themoviedb.org/collection/309259-naked-filmreihe?language=en-US )

But, on the set page ( https://www.themoviedb.org/collection/309259-naked-filmreihe?language=en-US ), it is listed that the set doesn't contain any movie.

So, is this movie part of the set or not ?

In the 2 cases, this is a Chinese movie. Perhaps, this is related to this.

And a third one with the same problem: Movie "Dumplings (2004)": https://www.themoviedb.org/movie/9060-jiao-zi?language=en-US Set "Three Extremes Collection": https://www.themoviedb.org/collection/498418?language=en-US Also a Chinese movie.

This happen also for the movie " Winners & Sinners (1983) ": https://www.themoviedb.org/movie/25539?language=en-US which is listed as being part of the set "Lucky Stars Collection": https://www.themoviedb.org/collection/300431-lucky-stars-collection?language=en-US But the set indicates that it contains 0 movie.

It appears that the problem have been solved.