Realtime: Listener not triggered on updates

I self host appwrite 1.8.1. The genereal functionallity works fine. But my realtime subscription isn't updating. I see "Received heartbeat response from realtime server" every couple of seconds. I had it working in the past but also not easily. Recently I switched from native nginx to nginx-proxy-manager. Maybe thats an issue? Websockets is enabled and why would the heartbeat work? I tried different channels. This is the basic code:

TypeScript

final subscription = Appwrite().realtime.subscribe([
      'databases.*',
    ]);
    print(
      'eventsListener: subscription created, channels: ${subscription.channels}',
    );

    Appwrite().subscriptions.add(subscription);

    subscription.stream
        .listen(
          (RealtimeMessage message) {
            print('eventsListener: received message');
            print('  channels: ${message.channels}');
            print('  events: ${message.events}');
            print('  payload: ${message.payload}');
          },
        )
        .onError((e) {
          print('eventsListener: stream error: $e');
          log('eventsListener error', error: e);
        });

    print('eventsListener: listening established');