Hey thanks for the additional input. I agree with your terminology, you're correct since I am still tying what I see on scopes to NTSC video terminology. Did I capture what you were asking for correctly? I do see the spikes in video you mention.
To answer your other questions, yes the streaks/tearing are always in the exact same line down from the top of the screen. I agree that an intermittent contact is unlikely but I too have no idea what else would fail at one line only. The rest of the picture is
perfect: no noise, clear image, good color, and even HiFi tracks every tape with aplomb. At least it sounds like I'm not the only one confuzzled.
I am using a Rigol DS1054Z, a digital scope, so I don't believe it would alternate between the inputs like an analog scope. I can take a closer look at the waveforms again to be sure they are clean. I will try to see what the other test points may show me, there are a few near the head output board and a bunch on the video board.