Apollo Client 3: query returns results in Chrome's Network tab, but undefined in my app

I am fetching some data using @apollo/client v3. In Chrome's network tab (http results), I can see it returns data and errors (I am not worried about the error, I know why it is right now.):

{
    data: {workItems: [,…]},…},
    errors: [{message: "Error trying to resolve position."
}

However in my app, data returns undefined.

Here's my client config:

export const graphqlClient = new ApolloClient({
    cache: new InMemoryCache(),
    link: ApolloLink.from([
        onError(({ graphQLErrors, networkError }) => {
            if (graphQLErrors) {
                graphQLErrors.forEach(error =>
                    console.log(
                        `[GraphQL error]: ${JSON.stringify(error, null, 2)}`
                    )
                )
            }
            if (networkError) {
                console.log(`[Network error]: ${networkError}`)
            }
        }),
        apolloLink
    ])
})

And my query:

gql`
    query WorkItems($ppm: String) {
        workItems(where: { ppm: $ppm }) {
            ...WorkItemKanban
        }
    }
    ${workItemFragment.workItemKanban}
`

const useWorkItemListDataGraphql = (args: {
    query: DocumentNode
    variables: { parent: string } | { ppm: string }
}) => {
    const { variables, query } = args
    const { data, error, loading, refetch } = useQuery<
        { workItems: WorkItem[] },
        { parent: string } | { ppm: string }
    >(query, {
        pollInterval: 180000,
        variables
    })
  
    // data returns undefined, but error shows the same error as in Chrome's network tab
    return { ...data, error, loading, refetch }
}

I am not sure where to start to identify what goes wrong. Loading the data works when there is no error, but I reckon this is not normal behavior, it should always load the same as I can see in Chrome's tab.