Priority values missing from firebase realtime database DataSnapshot

Question

I'm switching my app from firebase web (V8) to react-native-firebase. (I figured it would be less work to refactor than going to web V9) But I have run into a problem.

I use Priority values to store a value that indicates ordering of objects in a realtime database container, and when I read the snapshot the priorities are not there. It seems like the top-level snapshot has a priority value, but when I access the child snapshots with snap.child("child1') or snap.forEach(), the child snapshots do not contain a .priority property.

This is the code has been working in my app for over 5 years (with added debugging printouts).

  subscribeFB() {
      if (!this.unlistenFB) {
        this.unlistenFB = this.user.child('Counternames').on(
          'value',
          (snap) => {
            // Need to also grab the current timestamps when 
            // Counternames changes.
            this.getTimestamps(snap);
          },
          (error) => {
            info('Counternames subscription cancelled because', error);
          }
        );
      }
    }

    getTimestamps(snap) {
      this.user.child('Timestamps').once(
        'value',
        (tsSnap) => {
          setTimeout(
            () =>
              MultiActions.setCounters({
                counterSnap: snap,
                timestamps: tsSnap.val(),
              }),
            0
          );
        },
        (error) => {
          info('Could not get timestamps because', error);
        }
      );
    }
// Then in setCounters I use both snaps

 setCounters(snaps) {
  [...]
       if ( timestamps.sequence > this.state.timestamps.sequence) {
          debug('Getting new sequence from FB');
          // get sequence from FB
          var CounternameSnap = snaps.counterSnap;
          var cns = CounternameSnap.exportVal();
          debug(`CounternameSnap exportVal ${JSON.stringify(cns, null, 2)}`);

          var ch = CounternameSnap.child('-MH3NnGU5iM0eakrd7ZS').exportVal();
          debug(`Counter 44 exportVal ${JSON.stringify(ch)}`);

          CounternameSnap.forEach((ctr) => {
            var p = ctr.getPriority();

            debug(`Counter priority ${p} has key ${ctr.key}, val ${ctr.val()}`);
            // Do something with priority...
          });
 

When I change the order of the counters on another device, my .on listener triggers and I get the following printout:

 LOG  MultiStore:debug Getting new sequence from FB +2ms
 LOG  MultiStore:debug CounternameSnap exportVal {
  ".value": {
    "-MH3MqLK32gCi0pqBUg3": "Counter 33",
    "-MH4yucF8rmeewGbPAVI": "Counter 55",
    "-MH3NnGU5iM0eakrd7ZS": "Counter 44",
    "-NuBYkNVlAUIUeoQQCKA": "Counter 66",
    "-MGQOBLgEvEekOg6geQI": "Counter 11",
    "-MGzzZXdUwpBr8RlLLE-": "Counter 22"
  },
  ".priority": null
} +1ms
 LOG  MultiStore:debug Counter 44 exportVal {".value":"Counter 44"} +1ms
 LOG  MultiStore:debug Counter priority undefined has key -MGzzZXdUwpBr8RlLLE-, val Counter 22 +2ms
 LOG  MultiStore:debug Counter priority undefined has key -MH4yucF8rmeewGbPAVI, val Counter 55 +1ms
 LOG  MultiStore:debug Counter priority undefined has key -MH3NnGU5iM0eakrd7ZS, val Counter 44 +1ms
 LOG  MultiStore:debug Counter priority undefined has key -MH3MqLK32gCi0pqBUg3, val Counter 33 +0ms
 LOG  MultiStore:debug Counter priority undefined has key -MGQOBLgEvEekOg6geQI, val Counter 11 +1ms
 LOG  MultiStore:debug Counter priority undefined has key -NuBYkNVlAUIUeoQQCKA, val Counter 66 +1ms

This shows the top-level snap contains a .priority value (null) but the "Counter 44" child does not have the property at all. I can verify that the other device successfully pushed the new priorities to firebase: although the firebase console does not show priorities, I can export and download the container, and it looks like this:

{
  "-MGQOBLgEvEekOg6geQI": {
    ".value": "Counter 11",
    ".priority": 4
  },
  "-MGzzZXdUwpBr8RlLLE-": {
    ".value": "Counter 22",
    ".priority": 0
  },
  "-MH3MqLK32gCi0pqBUg3": {
    ".value": "Counter 33",
    ".priority": 1
  },
  "-MH3NnGU5iM0eakrd7ZS": {
    ".value": "Counter 44",
    ".priority": 2
  },
  "-MH4yucF8rmeewGbPAVI": {
    ".value": "Counter 55",
    ".priority": 3
  },
  "-NuBYkNVlAUIUeoQQCKA": {
    ".value": "Counter 66",
    ".priority": 5
  }
}

Is this exposing a previously unknown bug in my program, is it a bug in RNFirebase, a change in underlying FB V9+ iOS/Android libraries (It has the same problem on both platforms), or ???

react-native: 0.70.15

react-native-firebase: 19.1.1

[UPDATE:] I wondered if offline persistence might have something to do with this so I enabled persistence and found the problem remains the same either way.