Design flaw ? NO WAY !
If you got a scope. Set to display a BLANK, not even snow pix.
Be sure the G-2 is set proper. Color level at zero.
Look at the @200V should be clean. Same with the 3 video outs.
There almost HAS to be crap on them.
Check the E of the 3 outs for garbage also. Trace back.
There is a little PS that runs the EXT for isolation, Check that.
There is an "IF mute". didnt trace but probably turns off IF's when
on ext..
Dont forget the blanking stage also for a look-see.
Zeno