It seems that you are having some issues with your Slingbox PRO-HD since the TV signal is not good enough.
There are many things to take into account. In your case, I recommend you to check the Internet connection speed you are getting while the Slingbox PRO-HD is streaming the TV signal out of your network. Keep in mind that if you are trying to stream the TV signal using a HD TV source, the available bandwidth will be affected.
I recommend you to check the Slingbox PRO-HD requirements in order to determine if both ends (Slingbox location and remote location) meet the requirements for the Slingbox PRO-HD: