The Slingbox works with the network connection at the home. If you would like to watch High Definition video, you are required to have at least 2.0 Mbps (Mega Bites per Second) upload and download speeds at the home. Now these are the bare minimum requirements and some customers require more speed to work correctly.
For the buffering issue you are experiencing, you stated that you have an unstable network. Being that a Slingbox works with a home Internet connection and with the unstable network, the SlingPlayer for iPad will experience more buffering than usual because the network is not allowing the streaming to be received to the iPad correctly.
The only way to fix this issue is to contact your Internet Provider to see what they can do for your network.
Sling Media Moderation Team