So you have decided for some reason to host your WCF services with a net.tcp binding in IIS and for some reason the services timeout, becomes unresponsive or unreachable some times? It turns out this is a known Microsoft bug and the fix can be found here.
The problem is that the TCP listener service becomes unresponsive and if tcp port sharing is enabled the service might even crash.
References:
http://forums.iis.net/t/1167668.aspx?net+tcp+listener+adapter+stops+responding
https://support.microsoft.com/en-us/kb/2504602