All Manager Rules related to IS fired

As the title indicates almost everyday we are getting all Manager rules fired (IS related). I noticed that the issue is exactly same as what is described in http://advantage.webmethods.com/article/?id=SR-1-100154971

I need help to figure out the problem or direction on it. I have confirmed with network team and there are no apparent network issues. This was not close to any restart of application either.

The log I see is as below:

On the IS:
[ISU.0000.9999D] NotificationDispatcher.PingServerThread.connect dispatcher unregistered after ping timeout

On the Manager Server (which seems an obvious response to the above):
com.wm.ism.CommunicationException: java.lang.IllegalArgumentException: Dispatcher not found: 1214239776205

Please help!!

Development found it to be a bug, fixed in Manager_6-5-1_SP2_Fix3