ajax request it returns bad messages, it mixing messages from users

Hi I install the newest dev 4.x and there is bug. When user Alfa is goes to privateheartbeat stream on profile of user Beta and make shout, this shout sould be send only to Alfa user privateheartbeat stream but it is also send to Beta's stream. Then when Alfa is logout and Beta is login. On the first look the privateheartbeat stream of Beta has only Beta's messages but another issue is when is created first ajax request, because it also load the previous shout of Alfa user to Beta's private stream.
Sorry for my english