relay-style pagination cache not merging correctly

[Flusinerd]

Hello, I am having troubles getting Relay-Style Pagination to work:

This is how I implemented my document:

query MilestoneInstancesOfProject($projectId: ID!, $cursor: ConnectionCursor){
  milestoneInstances(filter: {projectId: {eq: $projectId}}, paging: {after: $cursor, first: 1}) {
    pageInfo {
      hasNextPage
      endCursor
    }
    edges {
      cursor
      node {
        resourceId
        ...
      }
    }
  }
}

Then I create a Service using the Codegen wich returns me a GQL Query.
I use this to generate a QueryRef.
Wich I then subscribe to to get all until there are no more instances:

const query = new MilestoneInstancesOfProjectGQL(this.apollo).watch({
      projectId,
});
query.valueChanges
      .pipe(
        takeWhile(
          val => val.data.milestoneInstances.pageInfo.hasNextPage === true,
          true
        )
      )
      .subscribe(async ({ data }) => {
        if (data.milestoneInstances.pageInfo.hasNextPage) {
          query.fetchMore({
            variables: {
              projectId,
              cursor: data.milestoneInstances.pageInfo.endCursor,
            },
          });
        }
      });
    return query;

The Cache is configured like this:

const cache = new InMemoryCache({
  typePolicies: {
    Query: {
      fields: {
        milestoneInstances: relayStylePagination(),
      },
    },
  },
});

When I check the Networks Tab in Chrome-Devtools I see it correctly triggering all HTTP Requests.
But when I check my cache using the Apollo Devtools it only contains a single MilestoneInstance

It looks like the merging doesnt work propperly.

Sincerely, Jan