FCM / APNs =>When specifying apns-collapse-id, old notifications on IOS devices are replaced by new one but new banner is always appearing

Question

(notification banner)

What is apns-collapse-id?

https://stackoverflow.com/questions/40009738/ios-thread-id-doesnt-group-push-notifications#:~:text=What%20is%20apns,it%27s%20for%20coalescing!

I am sending notifications to my Ios users(to ios devices) every x seconds. In this notifications I am informing users about current state of charging of their electric vehicles. Some of our users are complaining that notifications are annoying and they are popping up too often.

My goal is to replace old notification with new on without interrupting the user. (just replace the data, no sound, no new banner). On the server I specified apns-collapse-id in notification header. The new notification is replacing the old one but banner is appearing with every new notification and the user is annoyed.

Is this normal behaviour?

Is it possible to disable "banner displaying"? (Ideal behaviour would be to show banner just for the first notification).

On the server I am using FCM. The type of notification is Notification messages. Is it possible that this behaviour is bug in FCM?

message.Apns = new ApnsConfig
                    {
                        Aps = new Aps(),
                        Headers = new ReadOnlyDictionary<string, string>(new Dictionary<string, string>
                        {
                            {"apns-collapse-id", notification.ThreadId}
                        })
                    };