The 'cannot send data past enough' message means that somewhere between your encoder and the radio server there is something that is causing your data to get slowed down. This could be a faulty network card on your machine an improperly configured router or issues with the network connections. Also, if you're sharing your internet connection with other machines they could use a good chunk of your upstream bandwidth which can lower your upstream bandwidth.
Can you do a speedtest and check your upstream bandwidth next time you have a problem ?
There is also a thread here with some useful info :
My Radio is Buffering / Skipping