Push Notifications not forwarded to client

Hi,

we have an issue regarding push notifications from a back end server to the client through the F5.

There is a custom setup with an irule that redirects the uri /crm to a websocket (8081) on the back end server. The application in the back end should be able to send notifications to the client in the same session.

According to tcpdump I can see that the server sends the notification out through the active session (server:8081 -> SNAT-IP:xxxxx), but the F5 then doesn't forward this traffic to the client.

Any ideas, what could be the cause? There is no OneConnect in place.