I had the same issue with an old Philips Ambilight TV screen.
To fix this issue I used this command line in my /userdata/system/.xinitrc file :
xrandr --output HDMI-1 --mode 1280x720 --rate 60 --primary --set underscan on --set "underscan hborder" 20 --set "underscan vborder" 4
Change the values to get it works with your TV screen.