Use "tt17037878" as your example to see if you can replicate it.

https://i.imgur.com/NIentg0.png

This title is a co-production from Belgium, Netherlands, Germany and France. But it seems to only show up on filtering under "Belgium" (possibly for alphabetical reasons?)

Sci-Fi from Belgium: https://i.imgur.com/QqglgR6.png

Sci-Fi from Netherlands: https://i.imgur.com/9KxqK4x.png

Arcadia only listed under Belgium. Does the same if you filter by Germany and France.

I also tested it on some other titles and got the same result.

It's not a bug, it's a feature

When a movie is listed as coming from several countries, the country filter takes into account only the first one.

I agree this may look like a bug but the resulting list is way more useful this way.

Otherwise you'd have Matrix listed as an australian movie, etc...

It's not perfect but I've made this choice because the country filter was utterly useless otherwise.

Maybe I could put some hints...

Maybe replacing "- any country -" with "- any (first) country -"

What do you think? Any suggestions?

By "first" do you mean "first alphabetically"? Or do you mean you make a decision as to what the primary country is?

The countries are not in alphabetical order.

For example, Gladiator (2000) => USA, UK, Malta, Marocco.

It's not a perfect system but most of the time the first country tends to be the most relevant.

If you set the country filter to "Marocco", you don't want to get Gladiator listed, you rather expect a list of morrocan movies.

Sorry if I don't explain it well, hope you get what I mean.

Oh right, got it. I guess I understand this. Only thing I would add is that some productions are genuinely dual-production and genuinely make sense being listed under both countries.

I have no way to tell when it's the case or not. My solution is the best I could come up with.

Fair enough (I would add that this is a rarity anyway) So you have to make a decision on the "primary" country in each case where there's multiple countries listed on IMDB?

I take the first one listed on IMDb, that's all.