Complex filtering in GraphQL

I'm referring to this post: Complex GraphQL Filtering With neo4j-graphql.js

The "simple" filtering works as announced. However, as soon as I filter on a property of a dependent object in the graph, an empty result set is returned.

My schema has a customer type and an address type. My complex filter (I want to see only customers who have an address not in Germany) looks like this:

{
  CustomerOrLead(filter: 
    { address: { countrycode_not:"D"} }) {
    name
    role
    address {
      countrycode
      postalcode
    }
  }
}

Neo4j version is 3.5.12, "neo4j-graphql-js": "^2.6.0",
Any help is appreciated!

best regards,
Christoph

Hm, I just noticed that I'm not using @neo4j/graphql, so I'm going to give this a try.