HKWorkoutSession.sendToRemoteWorkoutSession doesn't report success or failure

We are seeing an issue where sending data using the asynchronous method HKWorkoutSession.sendToRemoteWorkoutSession(data: Data) will never return in some cases (no success nor failure).

This issue is happening for roughly 5% of Workouts started and will stay broken for the whole workout. The other 95% of the workouts, the connection works flawlessly. This happens on both watchOS 10 and 11, and with phones running iOS 17 or 18. The issue is quite random and not reproducible. Our app has thousands of workouts a day that use the workout session workout data send, with constant messages being send every few seconds.

In some of those 5% cases the "sendToRemoteWorkoutSession" will throw way later, like 30+ minutes later, if the watch app is awake long enough to capture a log of a failure.

Our code uses the same flow as in the sample project: https://developer.apple.com/documentation/healthkit/workouts_and_activity_rings/building_a_multidevice_workout_app

Here is some sample code, which is pretty simple.

Setup code:

let workoutSession = try HKWorkoutSession(healthStore: healthStore, configuration: configuration)
workoutSession.delegate = self
activeWorkoutSession?.startMirroringToCompanionDevice { success, error in
    print("Mirroring started on companion device: \(success), error: \(error)")
}
workoutSession?.prepare()

then later we send data using the workout session:

do {
    print("Will send data")
    try await workoutSession.sendToRemoteWorkoutSession(data: data)
    print("Successfully sent data") // This nor the error may be called after waiting extensive amounts of time
} catch {
    print("Failed to send data, error: \(error)")  // This nor the success may be called after waiting extensive amounts of time
}

So far, the only fix is to restart the phone and watch at the same time, which is not a great user experience.

Is anyone else seeing this issue? or know how to fix this issue?