One of our live sites are hosted on a load-balanced EC2 servers.  We have set up remote events via unicast UDP ports on web.config.  

One thing we noticed is that the concurrent editing notification (e.g. 'XxxxUser' is editing) sporadically appears.

I was testing using different browsers and different logins to test this:

1. On browser 1, I will update (not publish). Wait for auto-save notification.

2. Check browser 2 if notification is displayed.

As I mentioned, sometimes the 2nd user is notified, sometimes not.

What we guess is that, it seemed to work when the users happen to hit the same server.

Is there some configuration setting that we might have missed?

EPiServer Version: 7.5