Best Bets Problems

We have some issues with Episerver Find when using Best Bets.

We have an episerver installation (11.10.6) with episerver find (13.0.5).
In this installation there are 2 sites that use the same templates, the same code, etc.
domain1
domain2
We have created a "Best Bets" that we call "test1". When we point this to something Local to Domain1 (and run the code from Domain1) we get hit on it, but if we point it to something local on Domain 2 then we get no hit.
Same problem if we try to connect the "Best bet" to an "External link" = no result.
The code looks like this:

var query = EPiServer.Find.ClientExtensions.UnifiedSearch(SearchClient.Instance)
.For("test1");
query = query.UsingSynonyms();
var search = query.FilterByExactTypes(new List<System.Type>() {
typeof(Type1Page),
typeof(Type2Page)
// ...
});
search = search.ApplyBestBets();
search = search
.Skip(0)
.Take(100);
var myResult = search.GetResult(new HitSpecification { EncodeTitle = false, EncodeExcerpt = false });

Any ideas what we are missing here?