Sometimes when a nestream is published to FMS and recorded the first part of the stream stalls on frame one and then the rest of the stream plays out.

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);
}