Subgraph type not calling field resolvers

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,
1

As per my previous post, looking migrate a reasonably complex schema (examples below are extremely simplified) to federation. I’m coming unstuck where it seems a subgraph server is not completing the full resolver chain for a type. Any pointers to where I can start looking at would be great, I’ve not been able to determine the root cause.

Game subgraph

interface Game {
  id: ID!
  status: String!
  sport: String!
}

type BasketballGame implements Game @key(fields: "id") {
  id: ID!
  display_status: String!
  status: String!
  sport: String!
}

Feed subgraph

interface Consumable {
  id: ID!
  type: String!
}

extend type BasketballGame implements Consumable @key(fields: "id") {
  id: ID! @external
  type: String!
}

extend type Query {
  feed(user_id: ID!): [Consumable!]! 
}

The query response returns the Consumable array, and the __resolveType resolver runs correctly, and where appropriate the gateway server sends { __typename: 'BasketballGame', id: 'some_game_id'} to the __resolveReference resolver on the BasketballGame type in the Game subgraph (we may have other subgraphs with other types implementing Consumable). The display_status field has its own resolver, which takes some source data and generates the appropriate String response. This resolver is never executed. As that field is non-nullable, the Game subgraphs server throws errors to that effect. Strangely, the resolver for the status field, which exists on the Game interface, does run.