This is a normal occurrence. Wowza is disconnecting its side of a NetConnection when Wowza no longer senses the client that established that connection. House cleaning. So, by itself, this is not a problem.
This is most likely related to poor internet connections. And Wowza has to deal with lost connections, Wowza disconnects when it senses a lost connection. You do have control of this through the Application.xml /PingTimeOut and /ValidationFrequency settings. These are documented in the
The time (in milliseconds) that the server will wait for a ping response from the client. The ping mechanism is an RTMP internal ping (not an ICMP ping) that's used to validate a client connection. If set to 0, the server will wait indefinitely. If this value isn't provided (section commented-out), the value set in the VHost.xml file is used.
The time (in milliseconds) that the server will wait during server-to-client validation. Validation only occurs if the client stops sending data to the server. Validation is done by sending a ping request from the server to the client. If set to 0, the server won't validate client connections.