Code 9: Firebase Scheduled Export - 'The requested snapshot version is too old.'

I have encountered a new error that has recently occurred. As part of a scheduled backup function, I explore a copy go each datastore and save in a bucket for later use. The following syntax has worked well over the last year, however, I suspect due to load, has now stopped working.

async function getDataStore(collection) {
  return admin.firestore().collection(collection).get()
    .then(querySnapshot => {
      if (querySnapshot.size == 0) {
        console.log('No matching request for: ' + collection);
        return []
      } else {
        const data = [];

        //Query snapshot line throwing snapshot too old error.
        querySnapshot.forEach(doc => {
          let data_temp = doc.data();
          data_temp.doc_id = doc.id;
          data.push(data_temp);
        });

        return data;
      }
    });
}

This now throws a code 9, the requested snapshot version is too old. One way I can think of overcoming this, would be to batch the request into smaller 'chunks' and save. however, I wanted to see if there was something more efficient I may be missing. Fresh eyes are always helpful.

Thanks