Webhook content_state chat event weird behavior

Hello, since we are using our own notifications implementation using AWS amplify, we currently rely on the webhook to send Intercom notifications for our users. To send a push notification when creating a new chat message trough Proactive support we listen for the 'content_stat.chat' topic and stat_type: 'receipt'. 

However, for some users this event is only sent when they open the app, for other users (so far I could only make it work for one at a time) this event is sent even when they have the app on the background (which is the behavior I want). What is the behavior of this event, and how can I make it work for multiple users at the same time? I don’t want them to have the app open for this notification to arrive.

If listening for this event is not a reliable way of sending push notifications when chat messages are sent, is there any alternative way of making Intercom Notifications work alongside amplify notifications?