Hi There
This definately sounds like a bad connection, defective SCART lead or both. Have you tried using another lead ?
Regarding the Other player, I do not know of a way to go this as the only inputs to the TT box are Aerial and internet connections.
The best solution is to connect it seperately to your TV. You should have at least 2 SCART inputs on TV. If you have also an HDMI socket on your TV, your TTbox will work better if you connect via HDMI.