FLV recording stalling

The most common cause is related to not doing an accept client connection. Make sure that you have created a main.asc (or your application's name.asc) file with an appropriate application.acceptConnection(clientObject), otherwise some of the asynchronous callbacks will not work consistently for the NetConnection and NetStream methods, which may cause intermittent recording problems leading to playback problems.
Even something as simple as the following will work:
application.onConnect = function (clientObj)
{
this.acceptConnection(clientObj);
}