Guys thank you for your input on this.
It seems problem occurs only when lets say I'll setup the box on my TV with picture aspect ratio 16:9 but next guy has set to Original or similar. Also LG or Samsung TV's have option called "Just Scan" which kills Overscan, so if Just Scan is set to ON, there should be no problem between different TV's using same box.
Admin, you can close this topic. Thank you.